The gnome-shell plugin 3.4.1 in GNOME allows remote attackers to force the download and installation of arbitrary extensions from extensions.gnome.org via a crafted web page.

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.

Fedora 18 is found to be vulnerable to the blind command execution on the lock screen, and Fedora 19 is found to execute command through "Enter the Command" dialog box at the lock screen.

The issue is that in Fedora 18, when you open either the Activities panel or "Enter a command" dialog box (Alt+F2), and then lock the screen or let the screensaver lock the screen, then if you start typing on the lock screen, instead of entering the password or just waking the screen, it actually types anything you type on the Activities panel or "Enter a command" dialog box, so anyone who enters a executable command and press enter, the command is executed even when the screen is locked.

In Fedora 19, the "Enter the Command" dialog box is visible even after you lock the screen, so anyone can write the commands in the box and execute them over a locked screen.

The issue is still to be fixed and tested on Gnome Fedora 18 and 19 machines. KDE version were not found to be affected.