Microsoft confirms preview update KB5120998 can revert Windows desktop customizations

Microsoft has officially acknowledged that the August 2026 preview update identified as KB5120998 may cause desktop settings to be lost or reset on certain Windows devices after installation.

The update, rolled out as part of the monthly preview cycle for the latest Windows operating system, is intended to introduce security patches and feature refinements ahead of the final release. As a preview, it is distributed to Insiders and early adopters for testing before broader deployment.

Users who applied the update reported that personalizations such as taskbar arrangement, desktop wallpaper, icon placement, and other UI preferences reverted to default settings. The issue appears to affect a subset of hardware configurations, though Microsoft has not disclosed specific models or system requirements.

In a brief statement, Microsoft confirmed the problem and advised affected users to either roll back the update through the system's recovery options or wait for a corrective patch. The company emphasized that the bug does not impact core system functionality, but it does disrupt the user experience for those who rely on customized desktops.

The incident highlights the challenges inherent in the Windows update ecosystem, where preview builds are used to surface bugs before they reach the general public. Enterprises and power users often deploy preview updates to stay ahead of security threats, but they also accept a higher risk of encountering regressions such as this one.

Microsoft indicated that engineers are developing a fix that will be included in an upcoming cumulative update slated for later this month. In the meantime, the firm recommends that users back up their personalization settings or create a system restore point before applying future preview releases, a practice that can mitigate the impact of similar issues.