Microsoft has confirmed that the KB5070311 preview update is triggering bright white flashes when launching the File Explorer in dark mode on Windows 11 systems.
"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," Microsoft says in a Monday support document.
The bug is also triggered when navigating to or from Home or Gallery (including launching to Home), creating a new tab, toggling the Details pane on or off, and selecting 'More details' while copying files.
Microsoft is now working on a solution but hasn't provided a timeline for the fix. Until a fix rolls out, affected users are advised to switch off dark mode to avoid getting flash-banged when launching File Explorer or creating new tabs.
The fact that Microsoft hasn't caught and fixed this bug before releasing the KB5070311 optional update is quite surprising, given that it also rolls out with what the company describes as a "more consistent dark mode experience."
According to Microsoft, the preview update has refreshed the copy, move, and delete dialogs in both default and expanded views. Progress bars and charts now match the dark theme for better readability, and confirmation and error dialogs have been updated for a consistent appearance.
As BleepingComputer reported earlier today, KB5070311 also addressed a bug causing the explorer.exe process and the taskbar to stop responding after certain notifications.
With this update, Microsoft also fixed a known issue behind File Explorer search failures on some SMB (Server Message Block) shares after installing recent Windows updates.
In November, Microsoft confirmed another critical bug that causes File Explorer, the Start Menu, and other key system components to crash when provisioning Windows 11 24H2 devices with cumulative updates released since July 2025.
Last month, it also announced that it had started testing a new optional feature that preloads the File Explorer in the background to improve performance and launch times on Windows 11 systems.
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Comments
ken_smon - 4 weeks ago
'The fact that Microsoft hasn't caught and fixed this bug before releasing the KB5070311 optional update is quite surprising, given that it also rolls out with what the company describes as a "more consistent dark mode experience."'
Seriously? You find Windows update bugs 'surprising'?
Why would this surprise you?
Please go back through Bleeping Computer archives. You will find that basically every update from Microsoft broke something. And many did not actually fix the targeted issues, or actually made them worse.
b1k3rdude - 4 weeks ago
What the actual fck Micro$haft, I have to conclude that they are just fcking vibe coding at this point. 25H2 is a complete and utter sh!t show. Its like they have introduced the broken code that a number of web browsers seem to be infected with when launched.
@Sergiu Gatlan - what Ken said above, seriously dude, surprised..?
SwedgeLord - 3 weeks ago
Well, I guess it is a "preview" for a reason. The bugs were to be expected. However, this is one that does have to make you laugh. They decided to make a "more consistent dark mode Finder" And clearly nobody at Microsoft Dev/QC(?) uses Dark mode ever.
They'll ask the tester why he missed this and he'll say "if I mentioned every glitch in a patch you'd fire me!"