https://www.theregister.co.uk/2020/01/21/windows_7_black_wallpaper/

Microsoft has given Windows 7 users a parting gift with its last update as some holdouts are reporting existing desktop wallpaper being replaced by a sombre black screen – presumably in mourning for the veteran OS.

Others have also called out problems on Windows 10, but it is the venerable (and potentially vulnerable) 7 that is generating the most heat.