A flaw was discovered in gdm 3.24.1 where gdm greeter was no longer setting the ran_once boolean during autologin. If autologin was enabled for a victim, an attacker could simply select 'login as another user' to unlock their screen.
Exploitability
AV:PAC:LPR:NUI:RScope
S:UImpact
C:LI:LA:L4.1/CVSS:3.0/AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:LOther