On April 8, Microsoft released the latest cumulative updates for all supported Windows 10 and 11 releases. Besides your typical security fixes and improvements, KB5055523 for Windows 11 brought some unexpected changes to the system drive.
This month's security updates for Windows 11 create a new empty folder on drive C. It is called "inetpub," and it does not contain any extra folders or files. Its properties window shows 0 bytes in size and that it was created by the system itself. Neowin checked a bunch of Windows 11 PCs with the April 2025 security updates installed, and all of them had inetpub on drive C.
The mysterious inetpub folder is not protected, and you can remove it like any other folder on your computer. At the moment, it does not appear that deleting the uncalled directory causes any harm, nor does it affect any running processes or apps. You can also leave it as is since it does not take any space on your drive.
It seems that the newly discovered folder is related to Microsoft Internet Information Services, a platform that was introduced in 1995 for hosting websites and services. While IIS is still present in modern Windows releases, it is turned off by default. It is an optional feature that requires manual installation from the "Turn Windows features on or off" UI. Therefore, the inetpub folder should not be present on drive C by default.
Microsoft has not shared anything about the situation, so stay tuned for word from the company. This could be a simple bug that somehow slipped unnoticed into the public release. We will update the article once there is more information to it. Meanwhile, you can find release notes for Windows 11 April 2025 cumulative updates here.
Update, April 11 2025, 11.50 EST: Microsoft has confirmed in its security advisory that the inetpub folder was created after the April Patch against the CVE-2021-21204 escalation of privilege flaw. It has warned against deleting the folder. It writes:
After installing the updates listed in the Security Updates table for your operating system, a new %systemdrive%\inetpub folder will be created on your device. This folder should not be deleted regardless of whether Internet Information Services (IIS) is active on the target device. This behavior is part of changes that increase protection and does not require any action from IT admins and end users.
We have reached out to Microsoft about it asking for more details.
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