Ubuntu Security Notice 932-1 – Sebastian Krahmer discovered a race condition in the KDE Display Manager (KDM). A local attacker could exploit this to change the permissions on arbitrary files, thus allowing privilege escalation.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/88671/USN-932-1.txt
Source: https://packetstormsecurity.com/files/88671/Ubuntu-Security-Notice-932-1.html