Created attachment 147310 [details]
The window blocks user input to any other part of the Linux Desktop.
The only way to get rid of the pop-up window is to click on Abbrechen (No) or Korrekt (Yes).
Created attachment 147311 [details]
The window is very insistent and appears again if you close it by clicking No. Kleopatra is an attention seeker.
Created attachment 147312 [details]
Cert is invalid but not expired