Microsoft has confirmed that its August 2026 update preview for Windows 11 is causing some desktops to lose their personalisation settings, forcing affected machines onto a default black background that users cannot manually override. The bug affects Windows 11 24H2 and 25H2, and matters because it strips users of a basic customisation option with no available workaround, leaving them stuck until Microsoft ships a proper fix.

According to Microsoft's Windows release health dashboard, the issue prevents personalisation settings from loading correctly regardless of what values are stored, so the system falls back to black rather than honouring any user preference. Other desktop settings, such as slideshow options or contrast themes, may also be affected. Microsoft says it is working on a resolution for a future Windows update, but has not given a timeframe.