Since recent Plasma update, when suspending and resuming the session, there is a brief image of screen during resume that's showing what was on screen prior to suspend. Which essentially leaks some information about the previous session before lock-screen appears on resume. It looks like the screen buffer isn't filled with zeroes (or black rectangle) before suspend happens and that's coming back on screen before the lock. This happens both in Wayland and X11 session. Tested both with initiating suspend from Application Dashboard and from terminal with systemctl suspend. OS: Debian testing (Linux kernel 5.16.0). GPU: Sapphire Pulse RX 6800 XT. Mesa: 21.3.3 Systemd: 249.7 Not fully sure if it's a KWin bug or not, but filing under KWin component for now.
*** This bug has been marked as a duplicate of bug 316734 ***