The company says it used a KIR to implement the fix
Microsoft has confirmed that the issue causing certain operating system windows to flicker in Safe Mode on Windows 11 is now fixed. In an advisory published on April 29, Microsoft says File Explorer, Start menu, and Task Manager were all impacted by the screen flickering bug. The company has also confirmed that a previous cumulative update shipped to Windows 11 devices was the one to blame for the whole thing. “After installing KB5012643, devices starting in Safe Mode might show a flickering screen. Components that rely on Explorer.exe, such as File Explorer, Start Menu, and Taskbar, can be affected and appear unstable.
