"Authentication Required" when fast-switching between users

When using CTRL+ALT+Fx to switch to other user, I often receive a modal popup for which I do not own a password.

Who is “Sicer”? That could be the clue to your solution

Slicer is just the user I currently switched to, but this happens with any other

What happens when you supply “Slicer”'s password?

This happens when I enter the user’s (Slicer) shell login password:

Sir, … the screen shows that it is Slicer’s password that is required (no other user’s password)

It was Slicer’s password sir! …otherwise it would not be an issue (although annoying, I see no reason for these updates to be authenticated manually)

Perhaps you need to file a bug report against pam or polkit at https://bugzilla.redhat.com

OR

You haven’t quite explained the problem to my comprehension