KB5070312 Windows 11 23H2 Preview: SSU COSA AVD Fixes

Microsoft’s November 20, 2025 preview release for Windows 11, version 23H2 — KB5070312 (OS Build 22631.6276) — is a modest, quality-first cumulative update that pairs a non‑security cumulative LCU with a servicing stack update and a handful of targeted bug fixes. Delivered as an optional preview, the update’s stated goals are to improve functionality, performance, and reliability on 23H2 devices. The package includes corrected mobile operator profiles (COSA), several user-facing fixes for core file handling and File Explorer behavior, a Group Policy/AVD policy enforcement fix, and an updated servicing stack (SSU KB5071963). Microsoft lists no known issues with this release, but the timing — immediately after Home/Pro servicing for 23H2 has concluded — raises practical questions for home users and administrators about whether to install preview updates, how to stage them, and how to prepare for the Secure Boot certificate rollover that begins in mid‑2026.

Background / Overview​

Windows 11, version 23H2 entered mainstream servicing in 2023 and — for Home and Pro editions — reached its end of servicing on November 11, 2025. With Home/Pro no longer receiving routine security updates, administrators and consumers must plan migration paths to supported releases (24H2/25H2) to remain protected. KB5070312 is a non‑security preview update targeted at 23H2 devices and is offered as an optional download in Windows Update’s “Optional updates available” area as well as through the Microsoft Update Catalog and WSUS.
This preview contains two logical components:

• A combined servicing stack update (SSU) — KB5071963 — to ensure the update pipeline remains robust and reliable.
• A cumulative LCU (non‑security) that fixes discrete quality issues reported in production and testing.

Microsoft classifies this as a non‑security preview (optional). These preview builds are intended for early testing and quality assurance before fixes graduate into the next monthly rollup or security release where applicable.

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What’s in KB5070312 (quick technical summary)​

• Applies to: Windows 11, version 23H2 (all editions).
• Release date: November 20, 2025.
• OS Build: 22631.6276 (combined with servicing stack update KB5071963, version 22621.6265 for SSU).
• Type: Non‑security preview (optional).
• Delivery: Windows Update (Optional updates), Microsoft Update Catalog, WSUS import.
• Key fixes described by Microsoft:
  • COSA (Country and Operator Settings Asset) profile updates for certain mobile operators.
  • File Explorer: fixes an issue where File Explorer sometimes wouldn’t respond to mouse clicks until it was restarted.
  • File management: fixes an extraction error for .tar files when file/folder names contain more than 34 commonly used Chinese characters.
  • Group Policy and Configuration: fixes an issue where the HideRecommendedSection policy did not work in Windows 11 Enterprise multi‑session environments such as Azure Virtual Desktop (AVD).
  • Updated servicing stack (SSU) to improve reliability of future update delivery.
• Known issues: Microsoft reports no known issues for this release.

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Why this matters now​

Although KB5070312 is classified non‑security and optional, the context around it makes it noteworthy:

• Windows 11, version 23H2 Home and Pro reached end of servicing on November 11, 2025. That means consumer machines running those SKUs will not receive future security updates unless they move to a supported release. For organizations still on 23H2, Enterprise and Education SKUs will continue to receive updates through November 10, 2026, but consumer devices are effectively at the end of their consumer‑grade lifecycle.
• Microsoft is rolling out new Secure Boot certificates to replace expiring 2011‑era keys. Those certificates begin expiring in June 2026 and will affect Secure Boot update mechanisms and boot component security unless systems are updated to the new certificate chain.
• Servicing stack updates (SSUs) like KB5071963 are prerequisites for reliable future update installs. Installing the latest SSU as part of this combined package reduces the risk of update failures later.

For these reasons, even an optional preview package must be treated as part of a broader servicing and security plan — particularly in environments where many devices still run older builds.

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Deep dive: the tangible fixes and their implications​

COSA updates (mobile operator profiles)​

Mobile operator profile updates (COSA) are small but important for devices that rely on embedded SIMs (eSIM) or integrated mobile broadband. Profiles control operator provisioning, network parameters, and roaming behavior. When profiles are out of date, users can face connectivity or provisioning failures.

• Impact: Mobile devices, laptops with integrated WWAN, and some hybrid tablets.
• Operational note: These updates are low risk and generally safe to deploy, but enterprise imaging should be validated to ensure custom provisioning workflows are unaffected.

File Explorer mouse‑click fix​

A reported behavior where File Explorer does not register mouse clicks until the app is closed and reopened can significantly interrupt day‑to‑day workflows.

• Impact: All users who rely on File Explorer for navigation and file operations.
• Why it matters: Improving UI responsiveness reduces user friction and helpdesk tickets; this is a straightforward quality improvement.

.tar extraction fix for Chinese characters​

An edge case in the archive extraction logic caused failures when extracting .tar files that contain filenames or folder names with more than 34 commonly used Chinese characters.

• Impact: Users who share or receive archives with long Chinese filenames. This can affect content creators, international teams, and localized automation scripts.
• Operational note: If your environment uses scripts that create or extract tar archives with non‑Latin filenames, validate those workflows post‑update.

Group Policy: HideRecommendedSection not enforced in AVD​

Administrators who control device UI via Group Policy or Configuration Service Provider (CSP) discovered that the HideRecommendedSection policy did not suppress recommended content in Windows 11 Enterprise multi‑session environments like Azure Virtual Desktop.

• Impact: IT teams using AVD and multi‑session scenarios (such as education labs or virtualized shared workspaces).
• Why it matters: Enforcing a tailored UI experience is part of compliance and user experience; restoring policy operation prevents unwanted content and keeps controlled environments clean.

Servicing stack update (SSU KB5071963)​

The servicing stack component installs and manages Windows updates. SSUs are not uninstallable once combined with the LCU and are required for reliable future updates.

• Impact: All Windows Update operations on affected devices.
• Caveat: When the SSU is combined with the LCU into a single package you cannot remove the SSU via wusa.exe /uninstall; only the LCU portion can be removed via DISM by package name. Plan rollbacks accordingly.

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Installation and removal mechanics: practical notes​

• How to get it: Settings > Windows Update > Optional updates available; Microsoft Update Catalog; Windows Update for Business; WSUS (manual import).
• Combined package behavior: Microsoft combines the SSU with the LCU. The servicing stack (SSU) will remain on the system after installation and cannot be removed separately using wusa.exe.
• To remove the cumulative LCU after installation, administrators must:
  1. Use DISM to identify the LCU package name: DISM /online /get‑packages
  2. Use DISM /Online /Remove‑Package /PackageName:<LCU name>
• Recommendation: Do not attempt to remove the SSU. If rollback is necessary, perform system restores, image reapplication, or rebuilds per standard recovery procedures.

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Critical analysis — strengths​

• Focused fixes: The patch addresses concrete, user‑facing bugs that reduce friction in common workflows (File Explorer responsiveness, archive extraction, policy enforcement). These are narrow, testable improvements rather than sweeping behavioral changes.
• Servicing stack included: Bundling the SSU reduces a common class of update failures. Many organizations have experienced failed cumulative updates because the servicing stack was outdated, so this pairing is a behind‑the‑scenes stability win.
• Low immediate risk profile: Microsoft lists no known issues for KB5070312. The update is optional and non‑security, so administrators can validate it in a test ring before broader deployment.

Critical analysis — potential risks and caveats​

• Timing relative to 23H2 lifecycle: KB5070312 is a preview update for an OS version that — for Home/Pro — has already reached end of servicing. Installing optional preview updates on machines that are no longer receiving security updates may provide short‑term quality improvements but does not replace the need to migrate to a supported release. Consumers might misinterpret an optional preview as a substitute for full servicing.
• Preview updates can introduce regressions: Optional non‑security previews are not intended for broad production deployment. They are released for testing and feedback. Even when Microsoft reports no known issues, the very nature of preview software makes staged testing essential.
• SSU immutability: Because the SSU cannot be removed once combined, devices that install the package are committing to a servicing stack change. In the rare case of a subsequent SSU regression, administrators will have fewer rollback options.
• Localized edge cases: The .tar extraction fix is targeted but reveals how internationalization nuances can surface in unexpected places. Systems with automated archive workflows — especially in multilingual environments — should be validated carefully.
• Secure Boot certificate rollover: Although unrelated to this KB directly, the Secure Boot certificate migration campaign (new 2023 certificates replacing 2011 certificates beginning June 2026) represents a major future operational task. Failure to coordinate firmware or platform updates and certificate rollouts could result in boot‑time failures or loss of secure boot updateability.

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Recommendations — Home users​

1. Treat KB5070312 as optional testing software. If your machine is stable and you rely on it daily, delay installation until you can:
   • Create a full system backup or disk image, and
   • Schedule a maintenance window to test the update.
2. If you run laptops with WWAN/eSIM or rely on AVD, consider installing in a controlled window to validate connectivity and provisioning.
3. Plan to upgrade to a supported Windows 11 release (24H2 or 25H2). Home and Pro devices without continued servicing are exposed to future security risk; preview updates won’t change that.
4. If you do install and experience new issues, use System Restore (if enabled) or boot to a recovery environment and follow the DISM package removal instructions for the LCU if required.

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Recommendations — IT administrators and orgs​

Preparation and risk assessment​

• Add KB5070312 to a test ring for:
  • File Explorer behavior checks
  • Archive handling workflows that use .tar files with multi‑byte filenames
  • AVD policy enforcement tests (HideRecommendedSection)
  • WWAN/COSA provisioning verification
• Confirm firmware inventory and OEM guidance for Secure Boot certificate updates. Document machines that may require vendor firmware updates before June 2026 to accept the new certificate chain.

Deployment strategy (recommended)​

1. Test on a small pilot group (10–50 devices), including any devices that use WWAN/eSIM or are in multi‑session AVD environments.
2. Leverage Windows Update for Business deployment rings or WSUS to stage rollout. Import the update into WSUS and approve for test groups first.
3. Monitor telemetry and helpdesk volumes for 7–14 days before broader approval.
4. Maintain an image‑based rollback plan. Keep golden images updated for rapid redeployment.
5. Communicate to end users: clarify that this is a non‑security preview and does not substitute for a proper OS upgrade.

Patch and lifecycle planning​

• Prioritize migrations off 23H2 Home/Pro where possible. Document timelines for each device group and schedule upgrades to 24H2/25H2.
• For Enterprise/Education SKUs continuing to receive 23H2 servicing through November 10, 2026, maintain a lifecycle plan that includes phased testing of the Secure Boot certificate changes, firmware updates from OEMs, and eventual migration to a later Windows 11 baseline.

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Troubleshooting guidance (concise)​

• Install failure or update stuck:
  • Reboot and reattempt; if failure persists, check Windows Update logs and use the Windows Update Troubleshooter.
  • Confirm the servicing stack version matches KB5071963 if the SSU applied successfully.
• File Explorer still unresponsive:
  • Restart explorer.exe as a quick workaround: Task Manager > restart Explorer.
  • If persistent, collect Event Viewer logs under Applications and Services > Microsoft > Windows > Shell-Core.
• Archive extraction failures:
  • Verify the filename charset and length. Test extraction with an alternate archive tool (7‑Zip, tar CLI) to isolate whether it’s OS extraction logic or archive file corruption.
• Group Policy not enforced in AVD:
  • Confirm the policy is applied via RSOP and that AVD session hosts have received the latest policy definitions. Validate CSP policies are being delivered if using Intune.

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The Secure Boot certificate story — why it’s relevant to this KB and your update strategy​

Microsoft and OEMs will roll out new Secure Boot certificates (issued in 2023) to replace expiring 2011 certificates beginning June 2026. This certificate replacement is a foundational change to how firmware trusts boot components. If organizations delay preparing for the certificate roll, they risk:

• Inability to receive Secure Boot security updates after the expiring certificates lapse.
• Failure to validate certain boot components or third‑party bootloaders signed with newer certificates.
• Increased exposure to sophisticated boot‑level threats if devices are not updated before the expiration window.

Action items:

• Inventory devices by firmware vendor and platform to identify who will deliver certificate updates.
• Test certificate rollouts in lab environments and validate VMs vs physical devices. Some virtual platforms handle Secure Boot differently at the hypervisor level.
• Coordinate vendor firmware updates, imaging processes, and enterprise configuration policies to ensure the new certificates are applied ahead of June 2026.

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Final assessment​

KB5070312 is a narrow, responsible preview update that fixes discrete quality issues and refreshes the servicing stack for older 23H2 devices. For organizations still supporting 23H2, the package is safe to pilot and test — but it must be treated as part of a broader migration plan rather than a stopgap. The absence of known issues is encouraging, but history shows that even optional patches can reveal environmental regressions.
The broader context — end of servicing for Home/Pro 23H2 and the looming Secure Boot certificate rollover — makes this an inflection point. The update itself is low risk, but remaining on an unsupported or soon‑unmaintained baseline is not. The highest‑value steps right now are testing this preview in representative environments, accelerating migrations to supported Windows 11 baselines, and coordinating firmware and certificate updates before mid‑2026 to avoid boot or update disruptions.

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Quick checklist (for publication to internal teams)​

• Backup critical devices before applying preview updates.
• Add KB5070312 to a controlled pilot ring.
• Validate:
  • File Explorer responsiveness
  • .tar extraction with multi‑byte filenames
  • WWAN/eSIM provisioning and COSA behavior
  • AVD/Enterprise multi‑session policy enforcement
• Confirm SSU application and review Windows Update logs.
• Plan and document rollback steps (DISM removal for LCU; SSU is permanent).
• Inventory OEM firmware and plan for Secure Boot certificate updates (target: complete testing and deployment well before June 2026).
• Schedule OS upgrades for Home/Pro devices to 24H2/25H2 to restore full security servicing.

This preview is a good reminder that even small quality updates play an important role in maintaining a predictable Windows environment — provided they are deployed with staging, monitoring, and lifecycle awareness.

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Source: Microsoft Support November 20, 2025—KB5070312 (OS Build 22631.6276) Preview - Microsoft Support

 

[ChatGPT]

Microsoft has published the November 2025 optional non‑security preview update for Windows 11, version 23H2 — KB5070312 — delivering a small but focused set of quality fixes and a servicing‑stack update (SSU) for devices still on the 23H2 servicing branch.

Background​

Windows 11, version 23H2 has been in the maintenance cycle throughout 2024–2025, but Microsoft’s servicing calendar changed this autumn: Home and Pro editions of 23H2 reached end of servicing on November 11, 2025, while Enterprise and Education SKUs continue to receive security updates into 2026. That calendar context is essential because KB5070312 is an optional preview update released at the tail end of 23H2’s consumer servicing window. Microsoft published KB5070312 as a combined cumulative LCU plus an SSU component. The KB entry lists the targeted OS build for this release as OS Build 22631.6276 for 23H2, and it explicitly documents the fixes and the included servicing‑stack update (KB5071963). The update is distributed through the normal channels for preview updates: Windows Update (Optional updates), Windows Update for Business, Microsoft Update Catalog, and WSUS (manual import).

What’s in KB5070312 (high‑level)​

This November preview update is small in scope and focused on quality improvements rather than new consumer features. The official release notes call out these key fixes:

• Country and Operator Settings Asset (COSA): updated operator profiles for certain mobile carriers.
• File Explorer: resolved an issue where File Explorer sometimes failed to respond to mouse clicks until restarted.
• File management: fixed .tar extraction failures that occurred when file or folder names contained more than 34 commonly used Chinese characters.
• Group Policy / Configuration: corrected a regression where the HideRecommendedSection policy did not suppress recommendations in Windows 11 Enterprise multi‑session environments (for example, Azure Virtual Desktop).

The KB also includes a servicing‑stack update (SSU) identified as KB5071963 (servicing stack build 22621.6265), which Microsoft bundles to ensure the update can be applied reliably. The KB page warns that the SSU cannot be removed once installed, and it provides instructions for removing just the LCU portion via DISM if necessary.

Why this matters now (context and timing)​

• End‑of‑servicing pressure. Home and Pro devices on 23H2 passed the consumer end‑of‑servicing date on November 11, 2025; those devices will no longer receive monthly security updates going forward unless they are upgraded to a supported feature update (24H2 or 25H2). That creates a narrow window where optional fixes are still being published even as consumer servicing ends — a practical nuance administrators and power users need to understand.
• Preview updates feed the next security rollup. Microsoft’s cadence intentionally places optional non‑security preview updates two to three weeks before the next monthly security rollup; that preview can contain fixes that later become part of mandatory cumulative security updates. The “Windows monthly updates explained” guidance calls out that optional non‑security preview releases exist to surface and validate fixes prior to inclusion in a security rollup. Given that relationship, KB5070312’s changes could be folded into the next security update for supported versions or will already have been included for enterprise SKUs that remain supported.
• Insider and release preview footprint. KB5070312 was visible earlier in the Windows Insider/Release Preview channel rollout before appearing on the general Microsoft support page; initial Insider listings showed a slightly different build (22631.6269) in mid‑November, while Microsoft’s official KB documents show 22631.6276 on November 20 — a minor revision typical of preview → production transitions. That earlier Release Preview visibility is consistent with Microsoft’s staged validation model.

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Deep dive: the fixes and who benefits​

COSA updates (Country and Operator Settings Asset)​

The COSA change is targeted and typically affects cellular‑capable devices — laptops, detachables, and tablets with eSIM or SIM tray connectivity. Carrier profile updates matter for:

• Accurate operator names and connection metadata.
• Better carrier provisioning and potentially improved mobile data reliability on affected networks.

For organizations or consumers relying on mobile broadband, the COSA update can be a quiet but meaningful quality improvement. The KB lists this item explicitly under the “Improvements” section.

File Explorer responsiveness​

The File Explorer fix addresses a UI‑hang where mouse clicks in Explorer did not register until the app was restarted. This symptom can be disruptive to workflow (especially for users who rely on Explorer for file ops), and it’s the kind of issue that often gets reported widely in forums even when only a minority of users see it.
The resolution in this preview makes KB5070312 attractive to power users and IT helpdesk teams that have seen recurring Explorer unresponsiveness in their environments.

.tar extraction with long Chinese names​

The .tar extraction bug was localized and cultural in impact: extraction failed when file or folder names contained more than 34 commonly used Chinese characters. That’s a precise repro condition and one that affects users and organizations working with Chinese‑language archives. Fixing it improves cross‑locale interoperability and reduces risk of corrupted or failed extraction workflows in multilingual teams.

Group Policy: HideRecommendedSection in multi‑session​

This is the most enterprise‑facing fix in the update. Azure Virtual Desktop (AVD) and other Windows 11 Enterprise multi‑session scenarios rely on Group Policy and CSPs to control user experience. Customers reported that the HideRecommendedSection policy didn’t suppress recommendations in AVD; KB5070312 corrects that behavior so administrators can reliably enforce a cleaner Start/Recommendations experience in multi‑session environments. For managed desktop fleets and service providers, that’s an important compliance and UX improvement.

Servicing‑stack update (SSU KB5071963)​

The inclusion of SSU KB5071963 is notable because SSUs are foundational: they update the component that applies updates. Microsoft bundles SSUs with LCUs in many modern packages to ensure future updates are installed reliably. The KB includes the usual warning that the SSU cannot be removed once installed; administrators who use image management or need to minimize irreversible changes should read the KB’s removal guidance for the LCU portion and test in lab images first.

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Installation routes and practical steps​

KB5070312 is an optional preview update and is available via:

• Settings > Windows Update > Optional updates (Windows Update UI).
• Windows Update for Business (will show up in the Optional previews channel).
• Microsoft Update Catalog (standalone MSU download).
• WSUS (manually import from the Update Catalog).

If you choose to install it, recommended basic steps:

• Create a system backup or snapshot (especially for VMs or critical desktops).
• Test the update on a small set of representative devices (pilot group).
• Install via the method you use for that device type (Windows Update for casual devices; catalog/WSUS for managed fleets).
• Monitor logs and user reports for at least 48–72 hours for any regressions.
• If only the LCU portion needs to be rolled back, follow the DISM /Remove‑Package guidance in the KB — note the SSU cannot be uninstalled.

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Risks, caveats, and deployment guidance​

• End‑of‑servicing for Home/Pro: Home and Pro devices on 23H2 have reached the consumer end‑of‑servicing date. Installing a preview quality update does not extend security servicing. If you’re on a consumer SKU and have not upgraded to 24H2/25H2, the prudent long‑term action is to plan for a feature update to a supported version. Running preview updates on an end‑of‑servicing consumer build offers limited benefit compared with moving to a supported release.
• SSU permanence: The servicing stack component cannot be removed once applied. That’s standard, but it’s important — SSU changes are persistent and can complicate rollback strategies; for mission‑critical endpoints, test in images prior to broad rollout.
• Optional preview semantics: Optional non‑security preview updates are intended for validation and early deployment; they are not the same as monthly security updates. Microsoft’s guidance explains that preview updates may contain fixes that will later be folded into the next security cumulative update; they are cumulative and are offered only for the current supported versions. For organizations that require maximal stability, the usual advice is to pilot in a controlled ring and defer broad deployment until the fixes appear in a security rollup (where applicable).
• Automatic feature‑update pushes: Microsoft has also announced (and documented in release messages) that consumer devices on unsupported or end‑of‑servicing SKUs may be automatically upgraded to a supported feature update (for example, 25H2) to maintain security coverage. That’s a separate process from installing KB5070312 and is part of Microsoft’s device health / servicing enforcement for unmanaged consumer devices. If you prefer to remain on a particular branch, manage those devices through Windows Update for Business or enterprise configuration.
• Localization and driver interactions: The .tar extraction fix is locale specific; however, optional updates sometimes interact with third‑party software (archive utilities, AVs, driver installers). Test critical workflows that involve third‑party file management tools, mobile broadband manager software, and any custom Group Policy settings before deploying widely.

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Enterprise checklist (quick reference)​

• Inventory: identify devices still running 23H2 Home/Pro and flag for upgrade or remediation.
• Pilot: select representative test machines (including multi‑session AVD VMs) to validate the Group Policy fix and File Explorer behavior.
• Backup: snapshot images or create restore points prior to SSU deployment.
• Deployment path: publish through WSUS or Windows Update for Business for managed devices; use Microsoft Update Catalog for offline installs.
• Rollback plan: understand that the SSU is permanent — only the LCU portion can be removed with DISM if needed. Test DISM remove routines in lab.

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Where KB5070312 sits in Microsoft’s servicing model​

Microsoft’s servicing model differentiates a few update types:

• Monthly security updates (the “Patch Tuesday” cumulative security rollups).
• Optional non‑security preview updates (release channel “preview” packages typically aimed at validation).
• Out‑of‑band (OOB) updates for urgent fixes outside the normal cadence.
• Hotpatch / hotfix channels in specialized cloud scenarios.

The monthly preview (optional) mechanism intentionally surfaces quality fixes prior to inclusion in the mandatory security rollup, and customers can choose whether to adopt those previews early. Microsoft documented this process in its guidance explaining why preview updates exist and how they relate to security cumulative updates. KB5070312 is a typical example of that preview model in action. Microsoft also recently moved to simplified update titles (making the update names clearer and less cluttered with architecture/date prefixes) and announced there would not be a non‑security preview update in December 2025 (security updates continue as scheduled). Those administrative changes affect how IT teams identify updates in the UI but not the underlying content mechanics.

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Practical recommendation for different audiences​

• Power users / enthusiasts (single‑device, Home/Pro): If you rely on File Explorer heavily or have encountered the .tar/Chinese character extraction issue, installing KB5070312 from Optional updates is reasonable — but recognize that Home/Pro 23H2 has reached end of servicing, so prioritize a feature upgrade to a supported version to continue receiving security updates. Back up before installing.
• IT admins (enterprise fleets): Prioritize testing in a representative ring (including AVD/multi‑session scenarios) because the Group Policy fix for HideRecommendedSection matters for controlled UX deployments. Because SSU is included and permanent, validate image deployment and rollback plans in lab before broad deployment. Consider whether the same fixes will be included in the next mandatory rollup and, if so, whether to defer to that security rollup for a wider, lower‑risk deployment.
• Service providers / managed desktop teams: For multi‑tenant AVD or Virtual Desktop Infrastructure, this update fixes a configuration regression that can change the user experience; prioritize validating the policy behavior in a test tenant. Use Windows Update for Business rings or WSUS to control deployment timing.

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Notes on verification and minor discrepancies​

There are two related points worth calling out for accuracy and to avoid confusion:

• The Windows Insider Release Preview channel showed a prior build revision for the November preview (build 22631.6269) when it started appearing to Insiders in mid‑November; Microsoft’s KB page later lists the final SKU/build as 22631.6276 on the public support article dated November 20. Differences like this are common during the preview → public staging process and usually reflect minor repackaging or metadata revisions. Readers should treat the official KB page as the authoritative record for the public release.
• The KB and Microsoft guidance explain that optional preview updates are cumulative and will be folded into later security rollups for supported versions. However, for consumer SKUs that have hit end‑of‑servicing the practical effect is limited: the preview does not substitute for the ongoing security servicing you would get on a supported release. Treat optional previews on an unsupported consumer SKU as a short‑term quality patch rather than a long‑term maintenance strategy.

If there are platform‑specific or environment‑specific claims you want validated (for example, whether a particular OEM’s drivers or a specific backup agent has reported incompatibilities with the SSU), those should be tested in a lab, because public KB notes rarely enumerate every OEM or third‑party interaction and those interactions are often discovered only after broader deployment.

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Conclusion​

KB5070312 is a focused November 2025 preview update for Windows 11, version 23H2 that addresses several tangible quality issues — File Explorer responsiveness, a Chinese‑language .tar extraction bug, COSA carrier profiles, and a Group Policy regression for multi‑session environments — and it ships with a servicing stack update (KB5071963). The package is available now through Optional updates and the Update Catalog for organizations and advanced users who choose to test and adopt preview releases early. The strategic context matters: consumer Home/Pro devices on 23H2 reached end‑of‑servicing on November 11, 2025, so while the preview can deliver useful fixes, organizations and consumers must plan feature upgrades to a supported Windows 11 version (24H2 or 25H2) to remain protected with ongoing security updates. For managed fleets, a measured pilot → phased rollout remains the recommended path; for individual power users, the optional update is safe to try after backing up the device.

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Source: Microsoft - Message Center November 20, 2025—KB5070312 (OS Build 22631.6276) Preview - Microsoft Support

 

[ChatGPT]

Microsoft has rolled out an optional preview update — KB5070312 (OS Build 22631.6276) — for Windows 11, version 23H2, delivering a focused set of quality fixes and a bundled servicing stack update that matters to anyone still running 23H2 in production, test, or Release Preview rings.

Background​

Windows 11 follows a staged servicing model: feature updates ship annually while monthly quality and security updates are delivered through Patch Tuesday and optional preview channels. KB5070312 is a non‑security, preview cumulative update (LCU) paired with a servicing stack update (SSU) and is offered through the Release Preview/Optional updates path, Microsoft Update Catalog, and WSUS for manual import.
The timing of KB5070312 is significant because Windows 11, version 23H2 reached an important servicing milestone in mid‑November: consumer Home and Pro editions were moved out of mainstream consumer servicing, which changes how organizations and consumers should think about optional fixes versus security servicing. KB5070312 remains relevant for Enterprise, Education, and any devices still managed on 23H2, and it is visible to Release Preview Insiders who want early access to fixes.

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What KB5070312 Contains — Quick Summary​

• Applies to: Windows 11, version 23H2 (all editions where that branch is present).
• Release classification: Non‑security preview (optional).
• Target OS build: 22631.6276 (reports from Release Preview initially showed an intermediate build during staged rollout).
• Components:
  • Cumulative LCU (quality fixes).
  • Servicing Stack Update (SSU KB5071963) bundled to improve update reliability.
• Headline fixes:
  • COSA (Country and Operator Settings Asset): operator profile updates for certain mobile carriers.
  • File Explorer: fix for an issue where Explorer could ignore mouse clicks until it was restarted.
  • File management (.tar extraction): resolves extraction failures when filenames or folders contain more than 34 commonly used Chinese characters.
  • Group Policy and Configuration: restores the expected behavior of the HideRecommendedSection policy in Windows 11 Enterprise multi‑session environments (for example, Azure Virtual Desktop).

These are pragmatic, narrow-scope corrections rather than feature additions — the sort of maintenance changes intended to reduce helpdesk volume and correct regional or enterprise regressions.

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Overview: Why This Preview Matters Now​

Although KB5070312 is optional and non‑security, the package plays a few important roles:

• It addresses a highly visible UI bug (File Explorer ignoring mouse input) that directly affects productivity and helpdesk load. Fixing Explorer responsiveness can have an outsized return on daily user experience.
• The COSA updates are critical for devices using embedded or integrated cellular (eSIM/WWAN) because carrier profiles control provisioning and connectivity behavior. Updated profiles reduce provisioning failures and roaming problems on affected operators.
• The .tar extraction fix is an internationalization-focused correction; it prevents archive extraction failures for Chinese language filenames exceeding a precise character threshold. This improves cross‑locale workflows and reduces silent failures for teams exchanging archives.
• The Group Policy fix restores admin control for multi‑session images (AVD), which is important for service providers and enterprises running pooled or multi‑session Windows 11 images.
• Bundling an SSU (KB5071963) reduces the risk of update pipeline failures going forward, especially in images and managed environments that apply updates via WSUS/SCCM/Intune. However, SSUs are effectively irreversible through normal uninstall flows, and that immutability requires planning.

Taken together, KB5070312 is small in scope but high in practical impact for targeted audiences: VDI/multi‑session administrators, mobile‑broadband users, and any environment that has encountered the Explorer hang or the Chinese filename extraction bug.

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Deep Dive: The Key Fixes and Technical Implications​

Country and Operator Settings Asset (COSA)​

• What it fixes: Updates operator profiles used by Windows to provision and manage cellular connections (eSIM/WWAN).
• Impact: Laptops and tablets with integrated mobile broadband may experience improved provisioning, more accurate operator metadata, and fewer carrier-specific connectivity issues.
• Operational note: COSA changes are low risk but should be validated if your organization includes custom mobile provisioning scripts or specialized SIM workflows.

File Explorer — Mouse Click Responsiveness​

• Symptom: File Explorer sometimes wouldn't register mouse clicks (left or right) until the app was closed and reopened. This could make Explorer appear frozen while still rendering content.
• Why it matters: Explorer is the primary file management surface in Windows; input hangs directly affect user productivity and generate helpdesk tickets.
• Technical implication: Fixing Explorer input handling reduces user friction, but because Explorer integrates with third‑party shell extensions (cloud sync clients, antivirus, context‑menu extensions), administrators should pilot the update in environments that mirror production to catch interaction regressions.

File Management — .tar Extraction and Chinese Filenames​

• Symptom: Extracting .tar archives would fail when contained file/folder names used more than 34 commonly used Chinese characters.
• Scope: This is a relatively narrow repro condition but important for teams working with Chinese orthography or archives exchanged across global teams.
• Implication: The fix improves internationalization and cross‑locale reliability for archive handling. Environments that automate archive processing should validate extraction workflows post‑install.

Group Policy: HideRecommendedSection in Multi‑Session (AVD)​

• Symptom: The HideRecommendedSection Group Policy setting didn't suppress recommendations in Windows 11 Enterprise multi‑session images (Azure Virtual Desktop), even when set via Group Policy or CSP.
• Fix: Restores expected behavior so administrators can enforce a cleaner Start/Recommendations UX in multi‑session deployments.
• Importance: For service providers, enterprise IT teams, and multi‑session VDI administrators, restoring policy enforcement is crucial for predictable, compliant user experience. Validate the policy in pooled image scenarios after applying the update.

Servicing Stack Update (SSU KB5071963)​

• Role: The SSU updates the component that applies subsequent updates and ensures the update pipeline behaves reliably.
• Important caveat: Once an SSU is installed, it cannot be removed via the normal GUI uninstall path. While the LCU portion of a combined package can sometimes be removed via DISM, the SSU remains. This permanence should factor into rollback and imaging strategies.

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Distribution and How to Get KB5070312 (Practical Paths)​

• Windows Update (Optional updates): Check Settings → Windows Update → Optional updates. Insiders in the Release Preview will see earlier availability.
• Microsoft Update Catalog: Download the standalone MSU/CAB for manual deployment via WSUS, SCCM, or Intune. This is the preferred path for managed environments wanting controlled staging.
• WSUS/Windows Update for Business: Import or approve the package in your management tooling once the catalog entry is published.

Administrators should confirm the exact KB and OS build metadata in the Update Catalog before broad deployment; early Release Preview build numbers reported during staged rollout may differ slightly from the final optional package build. Treat build identifiers as authoritative only after catalog publication.

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Deployment Guidance and Recommended Steps​

1. Inventory: Identify machines on Windows 11 23H2 (Home/Pro vs. Enterprise/Education) and note which SKUs remain in commercial servicing.
2. Prioritize: Target pilot rings that include:
   • Representative hardware models.
   • Multi‑session AVD images and pooled hosts.
   • Machines that use integrated mobile broadband (for COSA validation).
   • Systems with third‑party shell extensions (cloud sync, antivirus, context menu hooks).
3. Backup/Snapshot: Create a snapshot or restore point for virtual machines and critical endpoints before applying the combined SSU+LCU package.
4. Pilot: Install KB5070312 on the pilot cohort and validate:
   • File Explorer responsiveness across common workflows.
   • Archive extraction (.tar) with sample Chinese‑language content and automation jobs.
   • HideRecommendedSection behavior in multi‑session images.
   • Mobile provisioning flows for WWAN devices.
5. Monitor: For 48–72 hours after pilot installs, monitor event logs, helpdesk tickets, and telemetry for regressions.
6. Rollout: Gradually expand to broader rings if the pilot is green. If issues occur, follow rollback guidance (see next section).

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Rollback and Remediation Notes​

• LCU removal: If you must remove the cumulative LCU portion, use DISM to enumerate and remove the package (DISM /Online /Get-Packages and /Remove-Package). Confirm the exact package name returned before issuing removal commands. The KB notes that only the LCU can be removed; the SSU will remain once applied.
• SSU immutability: Because the SSU component is persistent, plan imaging and rollback strategies accordingly. In environments where immutability presents risk, test thoroughly in isolated images before production rollout.
• Quick Explorer recoveries: For lingering Explorer hangs, use Task Manager → restart Windows Explorer or temporarily disable third‑party shell extensions to isolate conflicts. Collect logs and Feedback Hub traces if the hang persists after installing the update.

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Strengths: What KB5070312 Gets Right​

• Targeted, high‑impact fixes: The Explorer responsiveness fix addresses an immediately noticeable and productivity‑eroding bug. Delivering a focused correction reduces the chance of wide regressions while improving day‑to‑day use.
• Internationalization attention: Fixing the Chinese filename extraction bug signals attention to non‑English locale issues that can silently break workflows. This is valuable for global organizations and file exchange scenarios.
• Enterprise policy correction: Restoring Group Policy behavior for multi‑session images is crucial for VDI and service‑provider reliability.
• SSU inclusion: Bundled servicing stack updates improve the reliability of future updates and reduce the risk of failed installs in complex managed pipelines.

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Risks and Caveats — What to Watch For​

• Preview status: KB5070312 is a non‑security, preview update. By design it’s intended for testing and early validation and should not be treated as mandatory for production systems without a pilot.
• SSU permanence: Once the SSU is applied, you cannot uninstall it via the normal GUI path. Organizations must factor this permanence into rollback and image management strategies.
• Third‑party interactions: Explorer touches many third‑party extensions (cloud sync clients, AV shell hooks). The fix could surface new edge cases in particular hardware/software stacks — test across a representative matrix.
• Servicing timeline nuance: Home/Pro consumer SKUs on 23H2 have passed their consumer servicing window; installing preview quality updates does not replace the need to move to a supported feature update (24H2/25H2) to continue receiving security updates. Administrators and users should plan upgrades accordingly.
• Transparency gap: Microsoft’s public changelogs intentionally describe outcomes rather than line‑level fixes. For high‑assurance environments that require deterministic verification, this can be a limitation; functional validation in lab images is essential.

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Practical Recommendations — Who Should Install and When​

• Home users (consumer): If you are on 23H2 Home or Pro and you are not experiencing the Explorer hang or the other specific issues, prioritize upgrading to a supported feature update (24H2 or 25H2) because consumer security servicing for 23H2 has ended. Installing optional preview packages won’t restore security servicing.
• Power users and testers: If you previously used workarounds for the Explorer input hang (for example, restarting explorer.exe repeatedly), consider installing KB5070312 on a non‑production machine to validate improvements. Report residual issues through Feedback Hub.
• Enterprise/VDI administrators: Pilot the update in a ring that includes multi‑session images, integrated WWAN devices, and representative third‑party integrations. Confirm Group Policy behavior and mobile provisioning flows before broad rollout. Consider waiting for the cumulative Patch Tuesday rollup if you prefer extra telemetry and time for community validation.

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Verification, Cross‑Checking, and Unverifiable Claims​

The reporting around KB5070312’s initial Release Preview builds showed slight variation in the build number during staged rollout (22631.6269 initially reported in Release Preview), with the final optional KB listing showing 22631.6276. This kind of minor revision is normal during staged validation; administrators should confirm the exact build and package identifier in the Microsoft Update Catalog before mass deployment. This article’s summary is corroborated across community mirrors and Microsoft’s announcement pages; where minor discrepancies were observed in early listings, those have been flagged as typical staging artifacts. Any assertion about a specific build number prior to Update Catalog publication should be treated as provisional until catalog entries are confirmed.

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Final Assessment​

KB5070312 (OS Build 22631.6276) is a pragmatic, targeted maintenance release that addresses a set of tangible, real‑world problems: a disruptive File Explorer input hang, a localized archive extraction edge case for Chinese filenames, COSA carrier profile updates, and a Group Policy regression affecting multi‑session environments. The inclusion of an SSU is operationally sensible but increases the need for careful pilot and rollback planning because SSUs are persistent.
For most organizations, the right approach is deliberate: pilot the package on representative systems (including VDI pools and WWAN devices), validate policy enforcement and file workflows, and then either include the LCU in a controlled rollout or wait for the next Patch Tuesday cumulative if a more conservative path is preferred. Home and Pro users who are not experiencing the described problems should prioritize moving to a supported Windows 11 feature update rather than relying on optional previews.

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Quick Reference: Action Checklist​

• Check device inventory for Windows 11 23H2 endpoints.
• If affected by Explorer click hang or the .tar extraction issue, plan a small pilot.
• For managed fleets, obtain KB5070312 from the Microsoft Update Catalog and import into WSUS/SCCM/Intune for staged deployment.
• Snapshot virtual images and backup critical endpoints before applying the combined SSU+LCU package.
• Validate Group Policy behavior for multi‑session images (AVD) post‑install.
• Monitor telemetry and helpdesk reports for 48–72 hours after pilot installs, and be prepared to remove the LCU via DISM if necessary. Remember: the SSU portion cannot be removed via the GUI.

KB5070312 delivers meaningful day‑to‑day reliability improvements for specific, documented scenarios. When paced through a cautious pilot and validated in representative environments, the update is a sensible step to reduce user friction and restore predictable policy enforcement — just be mindful of the servicing and rollback constraints that come with SSU bundling.

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Source: thewincentral.com Windows 11 23H2 update KB5070312 available. Download Link.