(I have GNU/Linux and Microsoft Windows installed.) I played a game on Microsoft Windows, quit the game, restarted the PC, and selected GNU/Linux.
On the login screen, the background image was different, contorted, glitchy (similar to this image, but not as bad). On a closer look, it showed parts of the game I played … on the other OS, before the restart!
I could even "decrypt" some sentences, and various images were clearly recognizable (it might have been a sprite sheet, so technically only one image).
I guess this can be a privacy issue, especially because you’d typically expect that restarting and switching OS should "clear" traces like that (i.e., displayed content).
Is there someone at fault (software/OS or hardware)? Can you prevent this from happening somehow?
EDIT: It happened again (with a different game), and this time I made a photo: