js/ui/screenShield.js in GNOME Shell (aka gnome-shell) before 3.8 allows physically proximate attackers to execute arbitrary commands by leveraging an unattended workstation with the keyboard focus on the Activities search.

The automatic screen lock functionality in GNOME Shell (aka gnome-shell) before 3.10 does not prevent access to the "Enter a Command" dialog, which allows physically proximate attackers to execute arbitrary commands by leveraging an unattended workstation.