Since this pretty much defeats the purpose of locking a computer, allowing a non-user to force the system to logout, I'm marking this as a security vulnerability.
** This bug has been flagged as a security issue -- Pressing Ctrl+Alt+Backspace when the screen is locked kills the X session https://launchpad.net/bugs/68695 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
