The Hidden Threat of Windows’ ‘Inetpub’ Folder Post-Update: Security Risks and Mitigations

Something strange happened after Windows’ April update: a mysterious “Inetpub” folder began appearing across Windows 10 and Windows 11 systems, catching both casual users and seasoned sysadmins off guard. For many, this conjured up not fond memories of classic IIS deployments, but the more familiar feeling of “What fresh glitch is this?” Microsoft, in its usual style, hastened to explain—don’t delete it, it’s a security fix. But as with many “fixes” in the software world, the cure appears to have introduced a peculiar new symptom, possibly even a glaring vulnerability.

The Arrival of the Mysterious Inetpub Folder​

Let’s set the scene: It’s April, Patch Tuesday just rolled out, and you’re tidying up your file system with a fresh cup of coffee. Out of nowhere, there appears a folder called Inetpub in your root directory. No IIS installed, no web server in sight—just the silent arrival of a directory usually reserved for serving up websites in Microsoft’s Internet Information Services. For anyone whose last IIS deployment was back when dial-up was cool, this triggered nostalgia, confusion, and a healthy dose of suspicion in equal measure.
Microsoft wasted no time reassuring users that this was a “feature, not a bug,” an intended part of a security patch for the vulnerability CVE-2025-21204. Users were warned not to remove the folder; it was, allegedly, serving a higher purpose. The nature of that purpose, however, was left mostly to the imagination.
Now, pause for a moment to appreciate the irony: a folder original designed for managing internet content has become the unwitting mascot for the internet’s favorite pastime—debating Windows’ patch management.

How the Fix May Have Broken Security​

Enter Kevin Beaumont, security researcher and respected voice in the world of patch analysis. On his Double Pulsar blog, Beaumont dissected the unintended consequences of this newly deployed folder. The result? This so-called “fix” may have inadvertently created a gaping hole in system security, a sort of “open door” where previously there was only a window—pun entirely intended.
The exploit is surprisingly simple and doesn’t require admin privileges. Using the humble Windows command prompt, a user (malicious or simply curious) can leverage the MKLink command to turn the Inetpub folder into a junction point, redirecting it to another system file. For example:
MKLink /J C:\Inetpub C:\Windows\System32\Notepad.exe
This makes the path C:\Inetpub point to the Notepad executable. While this sounds like a harmless prank fit for a bored Friday afternoon, the real trouble is that, after such a modification, attempted installation of future security updates—including the one that placed Inetpub there in the first place—will fail.
Stop and think about that for a moment. We now have a scenario where a normal user, with only standard privileges, can essentially block Windows Update from ever doing its job again, leaving all future vulnerabilities unpatched. If this isn’t the IT equivalent of locking your house from the inside and throwing away the key, I don’t know what is.

The Anatomy of a New Attack Vector​

Let’s get into why this vectors matters. Historically, the creation of folders like Inetpub was handled with administrative oversight, part of a conscious decision to install a web server (IIS). But the April update unceremoniously dropped it onto all Windows machines, regardless of whether IIS was needed, wanted, or even supported. In so doing, it handed every user a new system object over which they retain unexpected—some might say excessive—control.
Here’s the crucial point: by making Inetpub universally available and susceptible to symbolic link (symlink) manipulation, Microsoft provided a pathway for malicious actors or mischievous insiders to block update mechanisms wholesale, without tripping UAC or other security alerts.
For IT pros already tearing their hair out over failed patch cycles, let’s be honest—this is nightmare fuel. One errant user, one clever script, one penetration tester hoping for a laugh, could leave an entire Windows fleet vulnerable, all thanks to a folder designed as a fix for something else.

Why Normal Users Should Never Have This Kind of Power​

If there’s a golden rule in OS design, it’s this: never give standard users the power to change the course of system updates. This basic tenant is as old as multi-user computing itself—user separation exists to keep systems stable and safe from unintended (or intended) meddling.
Microsoft’s blunder here is in setting permissions (or rather, failing to restrict them) on a folder with system-critical function. Allowing symlink creation by non-administrators on an update-essential path is akin to giving a programmer unsupervised access to the coffee machine—eventually, something’s going to explode.
From a real-world perspective, one has to wonder: Who at Microsoft greenlit this plan? Was it “Bring Your Intern to Work Day?” Or did a developer simply misread “publicly accessible” as “publicly editable”? If so, congratulations—now you know how a single oversight can ripple out across millions of endpoints.

The Unexpected Revival of IIS-Era Nostalgia​

Let’s not forget: the Inetpub folder isn’t new. It’s a legacy artifact from the days of Windows NT 4.0 (1996 for those keeping score). Traditionally, only systems with IIS installed bore this folder. Its sudden, unexplained arrival everywhere is a bit like finding a floppy disk drive has been added to your new laptop—it’s useless for most, confusing for many, and possibly dangerous if left unchecked.
For seasoned IT admins, this will evoke a wry grin. There’s a running joke that Microsoft never really deprecates anything; it just buries features in subdirectories and waits for someone to trip over them years later. In this context, the inexplicable return of Inetpub feels both on-brand and mildly alarming.

Documentation—MIA​

One of the strangest aspects here is the lack of clear documentation. Typically, Microsoft’s security team provides robust notes when altering system architecture, especially when it’s as visible as creating a root-level folder. In this case, users are left with vague reassurances and the strong suggestion not to delete anything. That’s not a confidence builder—especially for enterprise admins who require clear change logs and justifications for every tweak.
Let’s call it what it is: when your “fix” isn’t transcripted, and end-users are forced to reverse-engineer the intent, something has gone wrong in your communications pipeline.

Beaumont Raises the Alarm, Microsoft Stays Quiet​

According to reports, Kevin Beaumont took the responsible disclosure route. He informed Microsoft of the potential for privilege abuse and update blockade, and then waited. Two weeks later, the only sound was the gentle hum of millions of confused Windows machines (and perhaps the faint cackling of mischievous users finding ways to exploit this oversight).
Microsoft, always cagey about security admissions, remains silent—a move that will surprise no IT pro who has filed a support ticket since the Nixon administration. This reticence does little to bolster trust in the patch process. In fact, it diminishes the very confidence that Microsoft’s update cycle is supposed to instill.

The Real-World Impact on IT Operations​

So, what does this all mean for the average sysadmin, CIO, or IT consultant? Quite a bit. In the security world, anything that can be manipulated by non-administrators presents a risk for intentional sabotage, noncompliance, and possibly regulatory headaches. If a user exploits this loophole to block critical updates, a business could easily fall out of patch compliance—opening it up to attacks, fines, and a litigation parade nobody wants to attend.
Worse yet, for organizations beholden to strict update regimes—think healthcare, finance, or government—this bug is an especially cruel twist. If endpoints are rendered unable to update, entire fleets could become ticking time bombs, quietly accumulating vulnerabilities while rushing headlong into the next big exploit cycle.
Yes, the folder’s creation is technically reversible (you could hypothetically script a clean-up), but the risk remains that systems once sabotaged may never get patched again unless the underlying behavior is changed by Microsoft. Cue the frantic phone calls to Redmond and the “it worked yesterday” gaslighting in IT Slack channels worldwide.

A Masterclass in Unintended Consequences​

This episode is a live-action demo for the law of unintended consequences. In seeking to plug one security hole (CVE-2025-21204, for the record), Microsoft inadvertently pried open another—potentially far more damaging—attack opportunity. Moreover, introducing a change this visible, universal, and poorly documented smacks of rushed risk management, perhaps in response to shifting or unclear regulatory pressures.
We have patch cycles layered atop patch cycles, a growing backlog of folklore-worthy update issues, and now the inclusion of ye olde folders from yesteryear—reborn as cyber skeleton keys for mischievous users. For those chronicling the folklore of Windows upgrades, this one’s going straight into the annals.

What Should Microsoft Do Next?​

Let’s lay it out plainly: Microsoft must address this, and fast. The current state—where normal users can weaponize a security “fix” to block all future patches—is unsupportable for modern enterprise. Solutions abound and could be as simple as restricting symlink creation on critical directories, or updating their installer logic to ignore/repair corrupted or hijacked Inetpub directories.
Transparency is also in order. A clear KB article, laying out the necessity (or lack thereof) for the folder’s existence, the permissions rationale, and planned remediations would go a long way to rebuilding trust.
And, in a move sure to win applause from overworked admins everywhere—maybe next time, they could warn everyone first.

Lessons for IT Pros: Stay Paranoid, Stay Informed​

If there’s a single lesson to extract from all this, it’s that even the best intentions can go sideways in the world of patch management. A “simple” security fix can have devastating second-order effects, particularly when documentation lags behind rollout. For IT pros, that means remaining vigilant and skeptical—even (or especially) when the fix comes “straight from Microsoft.”
Proactively monitoring major system directories post-update is now a must. So is running regular integrity checks on critical folders. And perhaps, just perhaps, it’s time to revive that old playbook of denying write/junction privileges everywhere but where absolutely necessary.
Because if a simple empty folder can become the linchpin for disabling updates, imagine what else could be lurking in your next patch.

The Verdict​

At the end of the day, the inclusion of the Inetpub folder on every Windows box isn’t just a minor oddity—it’s a cautionary tale about how a hastily-deployed “fix” can create a systemic risk, particularly when it’s paired with a lack of communication and a naive trust in default permissions. For hardened IT veterans, it’s just another eyebrow-raiser in a long line of Microsoftisms. For the rest of us, it’s a reminder that even empty folders can be security time bombs—so keep your eyes peeled, your patches up to date, and your snark firmly in check.
After all, when it comes to Windows updates, sometimes the only thing more dangerous than old vulnerabilities is the patch designed to fix them. And if that doesn’t sum up the current state of enterprise IT, I don’t know what does.

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Source: Research Snipers Windows folder could be a great security risk – Research Snipers