Windows 11 October 2025 KB5066835 Triggers Taskbar and Search Failures

Microsoft’s October cumulative for Windows 11 — KB5066835 — has left a nontrivial number of PCs and servers with a broken taskbar, blank search panels, and even nonfunctional local web services, turning a routine patch into a widespread troubleshooting event that affects home users, IT administrators, and developers alike. The update shipped on October 14, 2025 and targets Windows 11 versions 24H2 and 25H2 (OS builds 26100.6899 and 26200.6899); Microsoft’s release notes confirm the package and note that it bundles servicing-stack changes as well as fixes and AI component updates.

Background​

Microsoft’s October 14, 2025 cumulative update (KB5066835) is a combined package that incorporates the latest servicing stack update (SSU) alongside the LCU (latest cumulative update). That bundling is important: when the SSU is combined into a cumulative package, it changes how removal and rollback behave — uninstall via the standard wusa /uninstall switch against the combined package will not remove the SSU component and therefore cannot be used to fully roll back the combined package in the normal way. Microsoft documents that behavior in the update release notes.
The patch was intended to deliver security hardening and quality fixes plus incremental feature and AI-component updates. But starting the day after the rollout, reports began to surface across social platforms and support forums describing several UI and service failures that map back in time to the same update. The trouble is not a single crash or driver fault: it spans taskbar icon rendering, the search UI, the Windows Recovery/Advanced Startup environment, local IIS/localhost web hosts, and — in some reports — Task Manager telemetry. The pattern of problems and breadth of affected subsystems make this a high-profile servicing regression for Microsoft and a real headache for administrators and power users.

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What users are reporting​

Taskbar icons missing or taskbar disappearing​

Multiple users posted that after applying KB5066835, many system tray and pinned app icons vanish from the taskbar. In several reports, only the active app icon remains visible; in more severe cases the entire taskbar disappeared, along with quick access to Wi‑Fi and notification controls. Restarts sometimes bring short-lived relief (for example: restarting explorer.exe or clearing the icon cache), but the issue reappears after a reboot for many affected machines.

Blank or black Search panel​

A widespread symptom is the search flyout or panel opening as a blank or black window with no content — the search box may be present but nothing loads beneath it. This affects both consumer machines and, according to multiple support threads, enterprise servers. Administrators have reported that Search stopped working entirely after mass-deploying KB5066835, and in at least some cases uninstalling the update restored functionality. Microsoft’s own support forum threads and Q&A responses show the issue was sufficiently common to generate a troubleshooting reply and suggested workarounds.

IIS / localhost and developer tooling problems​

Developers reported that local websites served by IIS or IIS Express stopped responding after the update, producing connection resets and HTTP/2 protocol errors. Microsoft staff and community answers have linked these failures to changes introduced by the cumulative update; some fixes and workarounds circulated quickly while others required rolling back the update. A Microsoft Q&A thread from October 15, 2025 acknowledges multiple reports and includes troubleshooting suggestions from Microsoft engineering staff.

Advanced Startup / recovery input breakage​

A subset of users reported that Advanced Startup (the Windows Recovery Environment) became unresponsive to USB keyboard and mouse input after the patch, blocking access to BIOS, Safe Mode, and repair options in situations where those inputs were required. Repairing or reverting the WinRE image restored functionality for some users, suggesting that the packaged recovery components deployed with the update may be implicated.

Other assorted telemetry and performance anomalies​

Beyond the headline issues, there are sporadic reports of Task Manager readings initializing to odd values, file preview failures in File Explorer, Windows Update install errors on some machines, and general sluggishness after installation. Those reports are less consistent but reinforce that this update introduced regressions across user-mode components and, in some cases, services closely tied to the networking and storage stacks.

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Why this looks more serious than a routine bug​

• The scope: multiple unrelated subsystems (Taskbar UI, Search, WinRE, IIS, Task Manager metrics) fail or behave incorrectly after the same update. That cross-cutting footprint suggests the update touches shared components (Search subsystem, explorer.exe behaviors, networking stack) that many features rely on.
• The packaging: because KB5066835 is a combined SSU+LCU, routine uninstalls are nontrivial and in some cases administrators found themselves forced to perform more invasive rollback operations. Microsoft warns that the SSU cannot be removed via the standard wusa uninstall for combined packages. That complicates recovery at scale.
• Enterprise impact: IT administrators reported wide-reaching effects on server fleets (search stopped on hundreds of servers in at least one posted report), causing major disruption for organizations that deploy updates at scale. Uninstalling the faulty update is not always a realistic or safe fix in production environments.

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What Microsoft has said (and not said)​

Microsoft’s public cumulative update notes for October 14, 2025 document KB5066835 and list the builds it applies to, along with the usual “how to get this update” and component-file lists. The release notes do not initially enumerate the regressions being reported in the wild; instead, the company has been engaging via support forums and Microsoft Q&A channels where engineers and community moderators have acknowledged specific issues — for example, IIS breakage and search problems — and proposed targeted mitigations such as registry-based workarounds.
A handful of official replies recommend registry changes (for example, creating or toggling DisableSearchBoxSuggestions under the Search registry path) as a mitigation for some search failures. Those mitigations have not been universally effective — several administrators reported the registry tweak did not restore search in their environments — and Microsoft’s responses vary thread-to-thread, which is typical during an active servicing incident. Where an immediate resolution was not available, staffers suggested rolling back the LCU on affected systems as a last-resort recovery.

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Confirmed and commonly-cited workarounds (what’s working for some users)​

Below are steps and mitigations that have been reported to restore functionality for many affected users; the effectiveness varies by environment and severity.

• Restart Windows Explorer
• Practical for the taskbar/search UI when the symptoms are local and transient: restarting explorer.exe can bring icons and search results back temporarily.
• Steps: use Task Manager → find Windows Explorer → right-click → Restart.
• Note: this is diagnostic and not a permanent fix if the underlying issue persists across reboots. Reports show a reboot often reintroduces the bug.
• Clear icon cache and rebuild search index
• These standard UI-repair steps can help when icon thumbnails or search results have corrupted caches.
• They’re worth trying for consumer PCs but they don’t address more systemic or server-side failures.
• Registry workaround: DisableSearchBoxSuggestions
• Open regedit as Administrator.
• Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Search
• Create a new DWORD (32-bit) named DisableSearchBoxSuggestions and set it to 1.
• Reboot.
• Some Microsoft responses and community posts suggested this setting as a mitigation for blank search panels, but multiple users reported it was ineffective in their environments. Use with caution and test before broad deployment.
• Uninstall the cumulative update (where feasible)
• For some impacted users, uninstalling KB5066835 restored services like Search and IIS. Several admins reported success with uninstalling the LCU to recover functionality in their fleets. However:
• This approach can be complex because the package is combined with the SSU. Microsoft documents that removing the combined package is not the same as removing only the LCU; wusa /uninstall on a combined package will not remove the SSU and may not fully revert changes. Enterprise teams should follow documented DISM removal steps and consult Microsoft guidance before mass uninstall.
• Apply specific security intelligence or Defender updates
• Community posts noted a case where installing the latest Microsoft Defender security intelligence update restored IIS functionality after other rollback attempts failed. This suggests additional, non‑LCU updates may address dependencies for affected services in some scenarios. Always verify with vendor guidance before relying on this approach.
• Use restore or imaging for severely broken machines
• In extreme cases where the system becomes unstable after the update, use a known-good system image or restore point to recover quickly, then block the offending update pending a fix. This is typically the practical approach for single-host recoveries but not ideal for large fleets.

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Step-by-step guidance for home users and power users​

• Assess severity
• If only a few taskbar icons or search tiles are missing and your machine is usable, start with non-invasive troubleshooting.
• Quick, low-risk steps
• Restart Explorer: Task Manager → Windows Explorer → Restart.
• Reboot and check if fix persists.
• Rebuild search index via Settings → Privacy & security → Searching Windows → More indexer settings → Advanced → Rebuild.
• Try the registry mitigation (test first)
• Back up the registry and create the DisableSearchBoxSuggestions DWORD under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Search and set to 1, then reboot. If it doesn’t help, revert the change.
• If Search/IIS/winRE remains broken
• Consider uninstalling KB5066835 via Control Panel → Installed Updates (if available) or run wusa /uninstall with the knowledge that the SSU may complicate full removal.
• If uninstall fails or is blocked, use System Restore or boot to a pre-update image if possible.
• Protect your data
• Before attempting any uninstall or image restore, ensure you have current backups for important files.

Caveat: Uninstalling patch-level updates may remove security fixes. Balance availability concerns with the security posture required on your device; if you revert the update, make sure compensating controls (firewall, network segmentation, up-to-date antivirus signatures) are in place until a corrected patch is available.

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Enterprise and IT administrator playbook​

• Immediate triage
• Identify and classify affected systems: user workstations vs servers vs developer machines hosting IIS or services exposed locally.
• If a critical server role (search index server, AD FS, local IIS) is impacted, escalate to the incident response lane — do not attempt mass uninstalls before evaluating the downstream dependencies.
• Test in a controlled environment
• Replicate the issue in a non-production ring and test the documented mitigations (registry workaround, Defender updates, or full uninstall) to determine the most reliable recovery path for your environment.
• Rollback considerations
• If rollback is required for multiple systems, prepare a scripted rollback process but be mindful that combined SSU packages change standard uninstall semantics. Use DISM remove-package patterns where required and validate with Microsoft support before bulk operations.
• Temporary mitigation (blocking)
• Use Windows Update for Business or WSUS to defer or block the offending update until Microsoft publishes a corrected package. Establish a test and validation window before re-deploying.
• Monitor official channels and apply fixes promptly
• Monitor Microsoft’s release health updates and the Windows Update Twitter/Release Health feed for a corrected LCU or out-of-band fix. When Microsoft publishes a fix, prioritize validation in your pilot rings and then stage broader deployment.
• Communication
• Inform impacted users of the status and recommended workarounds; provide instructions on how to restart Explorer or clear the icon cache safely. For developers using IIS, provide guidance on using alternative local web hosts or Docker containers until a permanent fix is released.

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Possible root causes — analysis and risk assessment​

A reliable root-cause determination requires Microsoft’s engineering-level telemetry, but the available evidence points to a few plausible scenarios:

• Shared component regression
• The update touches shared UI and search components (Search host, Shell/Explorer rendering, Search indexing, or a common runtime). A faulty change in a shared library could explain why the taskbar, search flyout, and other UI elements fail simultaneously. Historically, similar symptoms (Search panel black, taskbar anomalies) have appeared after other servicing flights, which reinforces the hypothesis that a shared UI/shim is the likely locus.
• Interaction with search indexing and configuration
• Microsoft Q&A replies and community notes indicate that conflicts between the updated search binaries and existing indexing configurations can cause search to stop rendering. That suggests the update may change how search enumerates or presents results, and existing configurations expose a regression.
• Network/security stack side-effects affecting IIS and WinRE
• IIS failures and WinRE USB input problems point to additional regressions located either deeper in the networking/protocol stack (e.g., HTTP/2 handling changes) or within recovery image components bundled with the update. Microsoft Q&A and community posts mention HTTP/2-related errors and WinRE image replacement as likely causes in some reproductions.

Risk assessment — why this matters:

• User productivity: missing taskbar icons and nonfunctional search directly reduce productivity for everyday users.
• Operations and security: admins are reluctant to remove a security LCU; yet widespread failure of services (Search, IIS) forces tradeoffs between security and availability.
• Update trust: repeated servicing regressions erode confidence in automatic patching for organizations and consumers alike.

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Historical context — this is not the first time​

Windows updates have occasionally introduced regressions in the taskbar or search UI in prior servicing cycles. Archives of past Insider and servicing notes show recurring known issues where search panels, taskbar icon rendering, and search-related flyouts behaved poorly after specific flights — a reminder that the Windows UI is tightly coupled and a small change in a shared component can ripple across many features. The pattern is recognizably similar to earlier incidents where a restart or rebuilding a cache temporarily restored functionality.
One historically observed mitigation was disabling Bing integration or web search in Windows Search on older Windows 10 builds, which in some narrow cases alleviated search-related instability. Modern Windows 11 search is architecturally different and the same registry or policy changes are not a panacea for the present regressions; they should be treated as experimental mitigations only after careful testing.

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What to watch for from Microsoft​

• Acknowledgement and KB update: Microsoft typically publishes an update to the release-health dashboard and a servicing advisory when a wide-reaching regression is confirmed. Expect an out‑of‑band LCU or an updated cumulative that specifically addresses the reported search/taskbar/IIS regressions.
• Clear rollback guidance: because of the combined SSU/LCU packaging, look for Microsoft to publish clarified rollback/remediation instructions if the uninstall path remains a commonly cited workaround.
• Patches and regressions: when the fix ships, validate the corrected package in a pilot ring before broad redeployment. Note that fixes for one symptom can sometimes introduce new behavior changes — always test with representative workloads.

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Final recommendations​

• For consumers: try the non-invasive steps (restart explorer, rebuild search index, test the registry mitigation) and only proceed to uninstalling KB5066835 if those steps fail and your machine is significantly impaired. Keep backups and be mindful that uninstalling a security update carries tradeoffs.
• For IT admins: isolate the issue in a controlled pilot, test Microsoft’s suggested mitigations (registry tweak, Defender updates), prepare an orchestrated rollback plan only after confirming the uninstall semantics for combined SSU+LCU packages in your environment, and block or defer the update in production rings until a corrected package is available.
• For developers: if local IIS/localhost stops working, try the Defender signature workaround reported in community threads, or roll back the LCU in a test image. Consider using containerized or VM-based local hosts to reduce dependency on host servicing during the immediate recovery window.

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Conclusion​

KB5066835’s October 14, 2025 rollout is a textbook example of how a broadly scoped cumulative update can introduce unexpected regressions affecting both consumer and enterprise environments. The symptoms — missing taskbar icons, blank search panels, IIS/localhost failures, and recovery environment input loss — are disruptive and, in some cases, difficult to remediate at scale because the update is delivered as a combined SSU+LCU package.
Short-term mitigations exist (Explorer restart, cache/index rebuilds, registry toggles, uninstall), but each carries caveats and inconsistent effectiveness. Enterprises should pause broad deployment pending a validated fix and follow Microsoft’s guidance for rollback and forensics. Home users should back up, try the low-risk mitigations, and weigh the security implications before uninstalling a security update.
This incident reaffirms the importance of layered defenses, staging updates in pilot rings, and maintaining reliable rollback and imaging procedures. Microsoft will likely issue a corrected package; the priority now for users and administrators is safe containment, methodical troubleshooting, and careful validation of fixes before redeploying at scale.

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Source: PiunikaWeb Windows 11 October update triggers taskbar, search problems

 

[ChatGPT]

Microsoft has confirmed that the October 14, 2025 cumulative update for Windows 11 — shipped as KB5066835 (OS builds 26100.6899 for 24H2 and 26200.6899 for 25H2) — introduced a serious regression in the Windows HTTP stack that can break localhost (127.0.0.1) HTTP/2 connections and has also been linked to a raft of secondary problems: File Explorer preview pane errors that block document previews, widespread installation failures with error codes such as 0x800f0922, 0x800f0983, 0x800f081f, 0x80071a2d, and 0x800f0991, reports of Logitech peripheral functionality loss, and even instances where mouse and keyboard input stops working inside WinRE (Windows Recovery Environment). Microsoft is rolling out mitigations and advising affected users to check for updates and reboot, while administrators and developers have deployed temporary workarounds and rollback strategies to keep systems and development environments running.

Background / Overview​

The October 2025 Patch Tuesday cumulative update for Windows 11 was presented as a routine security and quality rollup, delivering a number of new features and quality improvements across File Explorer, Narrator, Windows Hello and other components. The package combines servicing stack updates with the latest LCU and is mandatory because it contains security fixes.
Within hours of the update hitting mainstream systems, however, community reports and Microsoft support channels began to converge on the same pattern of failures: services and applications that depend on the kernel-mode HTTP listener (HTTP.sys) were failing to accept local connections, producing connection resets and HTTP/2 protocol errors. Microsoft acknowledged the regression and added guidance to its release health notes while engineering worked to issue targeted mitigations.
This article explains what is broken, why it happens, who it affects, the verified workarounds and emergency fixes available today, and the operational trade-offs administrators and developers must weigh before making changes to production systems.

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What’s broken and why it matters​

Core failure: HTTP.sys regression and localhost/HTTP/2​

At the heart of the problem is HTTP.sys, the kernel-mode HTTP stack used by IIS, HttpListener-based apps, and any server component that registers URL prefixes to be handled at the kernel level. The October cumulative update introduced a regression in the HTTP.sys path that mishandles HTTP/2 negotiation and TLS session setup for loopback connections. The result is that the kernel listener terminates or resets sessions prematurely and the client — browser, local service, or developer tool — receives immediate failures such as:

• ERR_CONNECTION_RESET
• ERR_HTTP2_PROTOCOL_ERROR
• HttpListener / IIS worker processes that never receive a single byte of the incoming request

Because HTTP.sys operates below the user-mode server process, a kernel-layer failure can make a perfectly healthy server process appear unreachable from the same host. This is why debugging tools, local devservers using IIS/IIS Express, edge cases like Azure AD callback handlers using loopback, and embedded appliance GUIs that expose a local web console are all impacted.

Secondary and cascading effects​

Beyond the kernel HTTP regression, the October update has been linked with several other disruptive behaviors:

• File Explorer preview pane: Some users see a security alert when selecting cloud-downloaded documents (for example, PDFs) in the Preview pane: “The file you are attempting to preview could harm your computer.” This blocks the inline preview functionality for files downloaded from OneDrive, Google Drive, or network shares.
• Installation failures: Multiple users report failures when installing the update itself or subsequent cumulative updates, surfacing error codes such as 0x800f0922, 0x800f0983, 0x800f081f, 0x80071a2d, and 0x800f0991. These codes typically indicate servicing stack / component store issues, or in some cases, rollback events when Windows Update reaches the end of its install script and aborts.
• Peripherals and drivers: A subset of users report Logitech special features (side-button mapping, keyboard macros) ceasing to function after the update. These appear to be user-space/driver-interaction regressions rather than an explicit Microsoft statement, but the timing is consistent with the update window.
• WinRE input failures: There are confirmed community incidents in which keyboard and mouse input stop working after booting into WinRE. A broken WinRE input stack prevents recovery and complicates in-place repairs.

Each of these outcomes carries different operational risk. For developers and administrators who rely on localhost bindings and IIS, the HTTP.sys regression is immediately blocking day-to-day work and service availability. For users relying on the Preview pane, the issue is an erosion of productivity. For IT shops managing fleets, installation errors raise the specter of incomplete rollouts, repeated failed workflows, and unnecessary downtime.

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How the problem manifests: common symptoms​

• Browsers show ERR_CONNECTION_RESET or ERR_HTTP2_PROTOCOL_ERROR when navigating to http://localhost or https://localhost.
• Visual Studio projects that use IIS Express fail to start, or the debugger cannot attach to breakpoints because binding or HTTP negotiation fails before user-mode handlers receive the request.
• Services using HttpListener, URL ACLs, or third-party products that embed local web servers (management UIs, appliance consoles) become unreachable.
• File Explorer shows the preview warning message for downloaded or cloud-hosted documents and refuses to show the embedded preview content.
• Attempts to install KB5066835 result in failure with error codes (for example 0x800f0922) and rollback; DISM/SFC show inconsistent results. Some systems require an in-place repair or an alternative install method.
• In WinRE, mouse and keyboard may be unresponsive after the update, blocking recovery operations that normally rely on those inputs.

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Verified mitigations and emergency workarounds​

There are several practical and verified approaches to restore functionality. Each has trade-offs and varying degrees of official endorsement from Microsoft. The options below are listed from lowest to highest impact.

1) Check for Microsoft’s emergency hotfix / Known Issue Rollback (KIR)​

• Microsoft has acknowledged the IIS/localhost problem and indicated a fix is being rolled out via update channels. A Known Issue Rollback (KIR) or an emergency patch can be delivered through Windows Update. Affected users should:
• Open Settings → Windows Update → Check for updates.
• Reboot the PC even if Windows Update reports “no new updates available” — the reboot can trigger the KIR logic or cause a pending update to be processed.
• This is the least invasive option and the preferred path for most users and administrators when the KIR is visible for the device.

Trade-offs: The KIR is targeted and typically safe. It may take time to propagate across regions and rings — some machines report the patch appearing within 48 hours, others needed an explicit check + reboot.

2) Update Microsoft Defender security intelligence​

• Several community reports show that installing the latest Security Intelligence Update for Microsoft Defender and rebooting resolved local HTTP issues for some systems. This is a low-risk step to try before more disruptive mitigations.

Trade-offs: Not a guaranteed fix; useful to try first because it is low-cost and fast.

3) Disable HTTP/2 in the kernel (temporary registry workaround)​

• The most widely used and repeatable workaround is to force HTTP.sys to not negotiate HTTP/2. This switches kernel-mode HTTP consumers to HTTP/1.1 and restores connectivity for affected localhost services.

Recommended commands (run elevated PowerShell or use regedit):
PowerShell variant:

New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\HTTP\Parameters' -Name 'EnableHttp2Tls' -PropertyType DWord -Value 0 -Force
New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\HTTP\Parameters' -Name 'EnableHttp2Cleartext' -PropertyType DWord -Value 0 -Force
Restart-Computer

Command Prompt / reg.exe variant:

reg add "HKLM\SYSTEM\CurrentControlSet\Services\HTTP\Parameters" /v EnableHttp2Tls /t REG_DWORD /d 0 /f
reg add "HKLM\SYSTEM\CurrentControlSet\Services\HTTP\Parameters" /v EnableHttp2Cleartext /t REG_DWORD /d 0 /f
shutdown /r /t 0

Important notes:

• This is a machine-wide toggle that disables HTTP/2 for all HTTP.sys consumers (not just IIS). Expect slower negotiation and some lost HTTP/2 capabilities until Microsoft ships a targeted fix.
• After the Microsoft fix is applied, you can remove those registry values or set them to 1 and reboot to restore HTTP/2 functionality.

Trade-offs: Effective and immediate for many users, but it is a broad workaround with performance and feature regressions for services that normally rely on HTTP/2. Use on development machines and carefully in production.

4) Uninstall the offending update(s)​

• If a machine cannot wait for a KIR or the registry toggle is unacceptable, uninstalling the October cumulative update (and, in some cases, the earlier preview that introduced similar behavior) will restore previous behavior.

Common uninstall commands:

wusa /uninstall /kb:5066835
wusa /uninstall /kb:5065789

• After uninstall, reboot and pause updates for several weeks until Microsoft confirms a new release that resolves the regression.

Trade-offs: Removing a security update leaves the machine with known vulnerabilities. Only do this when the operational impact of the regression outweighs the security risk and when compensating controls (network isolation, firewall rules) are in place.

5) Repair or reinstall via Media Creation Tool (in-place upgrade)​

• For machines encountering repeated installation errors that block patch application or create component-store corruption, the in-place repair upgrade using the official Media Creation Tool (MCT) or an official ISO can restore a healthy component store and allow the update to complete.

Recommended steps (high-level):

• Download the Media Creation Tool from Microsoft and use it to create an ISO or USB installer.
• Mount the ISO (or insert the USB) while logged into Windows.
• Run Setup.exe and choose the Keep personal files and apps option to perform an in-place upgrade / repair.
• Allow the process to complete and reboot.

Trade-offs: This is a higher-impact operation that takes time and requires administrative access. Back up important data before performing an in-place upgrade. It can resolve stubborn component-store issues that block Windows Update.

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Step-by-step remediation checklist (practical guide)​

• Pause and evaluate:
• If you depend on local IIS/IIS Express or local loopback services, assume risk until resolved.
• Communicate with team members and schedule remediation windows.
• Try low-impact steps first:
• Check Windows Update → Check for updates → Reboot.
• Install the latest Microsoft Defender Security Intelligence Update and reboot.
• Apply registry workaround (if required):
• Run the PowerShell commands above as Administrator.
• Reboot and verify localhost services function.
• If the system fails to install further updates or the problem persists:
• Attempt DISM and SFC as preliminary maintenance:
• DISM online restore health from a local ISO source is often more effective than default /RestoreHealth.
• Example:
• DISM /Online /Cleanup-Image /StartComponentCleanup
• DISM /Online /Cleanup-Image /RestoreHealth /Source:\sources\install.wim:1 /LimitAccess
• sfc /scannow
• If component store corruption persists, prepare for an in-place repair using MCT.
• For WinRE input failures:
• If WinRE is unresponsive to input, advanced users can replace WinRE.wim from a known-good 25H2 ISO and re-enable WinRE:
• Disable WinRE: reagentc /disable
• Replace c:\windows\system32\Recovery\winre.wim with the copy from the 25H2 ISO (mounted).
• Enable WinRE: reagentc /enable
• Only perform this if comfortable with WinRE internals; improper WinRE manipulation may block recovery options.
• If peripheral / Logitech features are broken:
• Reinstall vendor software (Options/Options+) and reboot.
• If problems persist, report to the vendor’s support channels and consider temporary rollback until driver updates are released.
• If you must uninstall the update:
• Use wusa to remove KB5066835 and pause Windows updates.
• Implement compensating security controls if rollback is required.

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Operational guidance for IT teams and developers​

• For development machines: prefer user-mode servers (Kestrel) or containerized/local servers that do not rely on HTTP.sys for loopback transport. Containerized environments reduce exposure to kernel regressions and make repro steps consistent across machines.
• For production servers: exercise extreme caution. The regression primarily affects loopback and kernel-mode HTTP listeners; if you run production IIS on Windows Server 2025 or Windows 11 server images, test carefully in a non-production environment and stage any KIR or hotfix before broad rollouts.
• For enterprise update management: monitor the Windows Release Health Dashboard and the Microsoft Update Catalog for KIR, SSU combined packages, and revised KB entries. Coordinate with security teams before uninstalling critical security rollups.
• For backup and image management: capture a clean image of a known-good system and keep recovery ISOs available for cases where updates produce irreversible component-store corruption on a device.

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Risks, limitations and what remains unconfirmed​

• Disabling HTTP/2 is a pragmatic stopgap but is not a long-term fix. Some production services may see degraded performance or behavior changes due to the lack of HTTP/2 features.
• Uninstalling a security update exposes the device to the very vulnerabilities Microsoft intended to fix. Rollbacks should be accompanied by compensating network-security controls.
• Reports about Logitech features and peripheral regressions are primarily community-sourced at this stage. While many users report identical timing with KB5066835, vendor statements are sparse; registry/driver interactions may complicate root cause attribution. Treat these as high-probability but not fully verified until vendor or Microsoft confirms them.
• WinRE keyboard/mouse failures have been replicated by multiple users and community responders; however, the precise vector (USB power state, driver initialization, or a buggy SafeOS component) is still being diagnosed. Replacement of WinRE.wim from a known-good ISO has restored functionality for many admins, but it requires comfort with low-level recovery tools.
• Installation error codes (0x800f0922, 0x800f0983, 0x800f081f, 0x80071a2d, 0x800f0991) are generic in some contexts and point to different underlying causes — component-store corruption, certificate or download issues, or interrupted servicing operations. Remediation may require dissimilar actions depending on the root cause; start with DISM/StartComponentCleanup and escalate to in-place repair if necessary.

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Best-practice recommendations​

• For all users: back up critical files, create a system restore point (where possible), and keep a recovery USB with the latest 25H2 ISO so you can perform an in-place repair if Windows Update leaves a system inoperable.
• For developers: adopt user-mode servers (Kestrel) or container-based workflows for loopback scenarios until Microsoft ships a permanent fix. When debugging, keep an alternative browser and verify whether the failure is HTTP/2-specific by forcing HTTP/1.1 in the client where possible.
• For IT admins: evaluate whether to pause automatic updates for a short window while Microsoft’s KIR or corrected cumulative update propagates. If business-critical servers are impacted, use the registry workaround in a controlled manner and plan to revert after the official patch is validated.
• For vendors and OEMs: prioritize driver and utility updates for input devices and peripheral-management software; users will expect vendor-side fixes that play nicely with the next cumulative security rollup.

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Conclusion​

The October 2025 Patch Tuesday cumulative update (KB5066835) delivered important security and quality improvements to Windows 11, but an unfortunate regression in the kernel HTTP stack produced a disruptive real-world failure mode for localhost HTTP/2 and a suite of related issues. Microsoft has confirmed the problem and is rolling out mitigations, while the community and support channels have converged on practical workarounds — most notably the registry toggle that disables HTTP/2 for HTTP.sys and targeted remediation via Microsoft Defender intelligence updates or an official Known Issue Rollback.
Administrators and developers should assess the risk and impact to their environments and apply the least invasive remedial action that addresses their operational needs. For many, the recommended path will be: check for Microsoft's emergency fix and reboot, then — if necessary — apply the registry workaround or proceed to controlled rollback or in-place repair. All such steps should be performed with backups and compensating security measures in place.
Windows updates are crucial for security but occasionally carry unexpected side effects. This episode is a reminder to adopt resilient development and operational patterns — containerization, user-mode local servers, and staged update deployment — that reduce exposure to kernel-level regressions while allowing security updates to continue to protect systems.

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Source: Windows Latest Microsoft confirms Windows 11 KB5066835 issues. Localhost, File Explorer preview, install errors