Microsoft says the September 2026 Patch Tuesday updates fix a known issue causing desktop settings to be lost or reset on some Windows devices.
The company confirmed last week, after a wave of user reports that their wallpaper switched to a black background automatically, that this bug is triggered after installing the KB5120998 August 2026 preview update on Windows 11 24H2 and Windows 11 25H2 systems.
"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 affected devices, attempting to manually restore customized settings does not work. This is because the issue prevents the correct loading of settings, regardless of their value. In this case, a default black background is used instead."
The KB5120998 preview update causing this issue also changes or resets mouse settings, making it impossible to restore the previous settings after they are reverted.
While this is an optional update that requires users to click the "Download and install" link, it may also install automatically if the "Get the latest updates as soon as they're available" option is enabled.
On Tuesday evening, after releasing this month's Patch Tuesday cumulative update, Microsoft said the issue has been fixed and advised users to update their devices.
"This issue was resolved by Windows updates released September 8, 2026 (KB5124008), and later. We recommend you install the latest security update for your device as it contains important improvements and issue resolutions, including this one," it noted.
Microsoft addressed a similar issue six years ago, in February 2020, after the KB4539602 Windows 7 update broke desktop wallpaper functionality and caused wallpapers in 'Stretch' mode to display a blank black screen.
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