"Following installation of Windows updates released August 27 2026 (KB5120998) and later, some Windows Desktop settings fail to load, resulting in desktop backgrounds displaying as a solid black color," Microsoft said in a Windows release health update on Wednesday.
Microsoft's Windows release health update
Microsoft confirmed the problem in a Windows release health update that followed user reports. The company said the bug can prevent the correct loading of desktop settings and that, on affected devices, "a default black background is used instead." The advisory also states that attempting to manually restore customized settings does not work because the underlying issue prevents settings from loading "regardless of their value."
Affected systems: Windows 11 24H2 and 25H2
The known issue is limited, according to Microsoft, to systems running Windows 11 24H2 and Windows 11 25H2. The company tied the onset of reports to the August 27, 2026 preview update KB5120998 and later updates derived from it.
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Fix the backlogUser-facing symptoms: wallpaper, themes, and mouse settings
Initial wave reports focused on wallpaper changes: users found their desktop background switched to a solid black color after installing KB5120998. Microsoft expanded the list of symptoms one day after the update's release, acknowledging that the preview update also changes or resets mouse settings and that affected users are "unable to restore the previous settings after they are reverted."
Microsoft's notice explicitly identifies other desktop elements that may be impacted, including slideshow settings and contrast themes. The description makes clear the problem is a loading failure rather than a simple configuration overwrite: the system fails to load the saved values and falls back to a default black background.
How KB5120998 is delivered
KB5120998 is a preview, optional, non-security update that Microsoft released on August 27, 2026, and that included Start menu, taskbar, and Windows search improvements for Windows 11 versions 25H2 and 24H2. Because the update is optional, it requires a user to click the "Download and install" link to apply it. However, Microsoft notes an exception: systems that have the "Get the latest updates as soon as they're available" option enabled will receive the preview automatically, without manual selection.
What this means for end users and IT teams
- End users: Those who installed KB5120998 reported their wallpaper switching to a black background and, in some cases, loss or resetting of other desktop and mouse settings. Microsoft warns that, on affected machines, manual attempts to restore customized settings do not succeed because the issue prevents the correct loading of settings.
- IT and support teams: Administrators managing fleets that run Windows 11 24H2 or 25H2 will likely need to identify machines with KB5120998 applied and track user reports of desktop and mouse-setting regressions. Because the company frames the problem as a failure to load settings rather than a reversible overwrite, the outage implies that post-install restoration efforts may not return devices to prior configurations until Microsoft provides a corrective update.
This is not the first time a Windows update has produced black wallpaper as a visible symptom. Microsoft addressed a similar bug in February 2020, after KB4539602 broke desktop wallpaper functionality and caused Windows 7 wallpapers in "Stretch" mode to display a blank black screen. The 2026 preview update and its immediate aftermath underscore how changes intended to refine UI elements, such as Start and taskbar improvements, can produce widely visible regressions when a loading path fails.
Microsoft's advisory documents the problem and its immediate effects, but it does not include a timeline for a fix in the published update notice. Whether Microsoft will issue a corrective update that also restores users' custom settings, or how restoration will be handled technically, remains an open question.
Original reporting: https://www.bleepingcomputer.com/news/microsoft/microsoft-says-kb5120998-windows-update-resets-desktop-settings/
