[Bug 71619] Locked session becomes temporarily visible during user switch

[LxP]

Public bug reported:

Binary package hint: gnome-screensaver

Hello,

If I select System > Quit > Switch User, my session locks and I am
presented with the login screen.

When I select Quit from the login screen, my monitor briefly goes black,
my desktop is fully redrawn (this takes one full second on my PC) and
then my screen saver is displayed.  This behaviour can also be exhibited
by locking the session, switching to another TTY (regardless of its
content) and then switching back.

As my session is locked, I would expect my desktop not to be displayed
under any circumstance besides correct entry of my password.  I have
marked this as a security vulnerability since a user's desktop may be
displaying sensitive information at the time that it is locked, and it
is possible to glance at that information without unlocking the desktop.

** Affects: gnome-screensaver (Ubuntu)
     Importance: Undecided
         Status: Unconfirmed

** Visibility changed to: Public

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Locked session becomes temporarily visible during user switch
https://launchpad.net/bugs/71619