Microsoft’s buggy Windows 11 update KB5070311 (build 26200.7309) is breaking File Explorer dark mode

• Windows 11 builds 26200.7309 and 26100.7309 for version 25H2 and 24H2 roll out to everyone with a bug that breaks File Explorer.
• After installing this update, when opening File Explorer, the app will display a giant white flash before loading files.
• Microsoft is working on a fix, but such a bug should have been fixed before arriving in the Stable Channel.

Microsoft is now rolling out the Windows 11 December 2025 update, builds 26200.7309 for version 25H2 and 26100.7309 for version 24H2 (KB5070311), which introduces a refreshed dark mode experience for File Explorer, but the improvements also ship with an unexpected bug that breaks the theme.

The company is expanding dark mode support across more system dialogs in File Explorer, including for copy, move, delete, and error prompts, now aligning more closely with the system dark theme. Progress bars, charts, and confirmation dialogs for actions such as skip and override have also been visually updated to reduce design inconsistencies in the operating system.

Despite the visual improvements, Microsoft confirms that the update breaks the dark mode experience. Users launching File Explorer in dark mode may see a sudden white flash before the interface finishes loading.

According to Microsoft’s release notes, “After installing KB5070311, you might experience issues when opening File Explorer in dark mode. The window might briefly display a blank white screen before loading files and folders.”

This isn’t the only known issue in the update. Microsoft also warns that the password icon may fail to appear under sign-in options on the Lock Screen, which could confuse users relying on password authentication.

The company says it’s actively working on fixes, but quality-control concerns continue to grow. These types of problems would typically surface earlier through the Windows Insider Program’s Release Preview Channel, which is designed to catch stability issues before updates reach general availability.

While staying current with security patches and system improvements is essential, you can still pause or completely disable automatic updates until Microsoft addresses these issues.

Aside from these problems, the last cumulative update for Windows 11 also ships with a slew of new features and other improvements. For example, in this update, the Windows Search panel now matches the dimensions of the new Start menu, and you can change Spotlight wallpapers from the desktop context menu.

Microsoft is also adding an option to disable the Drag Tray feature, porting more keyboard and mouse features from the Control Panel to the Settings app, and the Mobile Devices options are now part of the Settings experience. 

This cumulative update is also improving the “About” settings page, adding a new “Virtual Workspaces” page to control virtualization features from the Settings app, and Microsoft is bringing the Xbox Full Screen Experience to more handheld devices.

Finally, this update also brings a new Widgets dashboard design, as well as other features, improvements, and fixes.