Microsoft's Windows Hello face unlock feature no longer works in dark rooms, and that's not a bug. Microsoft quietly made changes to Windows Hello in April to fix a Windows Hello spoofing vulnerability. Fixing this security flaw has now resulted in the removal of critical Windows Hello functionality in Windows 11.
Some Surface Laptop users have noticed that they can no longer log into their laptops using facial recognition in a dark room, which Microsoft said in its April Windows Update patch notes:
If you disable your webcam in Windows 11 Device Manager, Windows Hello will continue to work in a dark room, but that means you won't be able to use the camera in any apps or video calls. This is a workaround if you're only using the camera to unlock your laptop, but most people will want the camera to work within video calling apps.
Microsoft uses a combination of color cameras and infrared sensors to detect faces for its Windows Hello feature. The security flaw, discovered by Nanyang Technological University and rated "important" by Microsoft, has not yet been publicly disclosed or exploited. Microsoft even said that it was "less likely" that a malicious actor could exploit the vulnerability locally on the device.