Comment 27 for bug 1044549

This 8-years problem still exists on 20.04 (!)

As commented in #4 back in 2012, the particular focus-mode triggers crazy situations.
Ex: autologin + autostart app's and/or auto-move windows (dedicated desktop per window)

After GDM (auto)login, the "gcr-prompter" can not be focused or even worst: not even visible. But still holds a TOTAL focus (grabbing all inputs).
That means neither the popup nor the session can be closed, Gnome-shell can't be restarted, and the only possibility is to switch to tty, use `ps`, determinate the name of the process... what not even a workaround for a normal user.

I think there is no reason that justify keeping a user from using "Alt-F2 / restart".

About why this popup start in the first place is, IMHO, not a subject (I've 1 owncloud + 2 google accounts there and I can't tell why this come up)
... But *if* this popup arises it must not brick the whole session.