Ubuntu Security Notice 1950-1 – It was discovered that Light Display Manager created .Xauthority files with incorrect permissions. A local attacker could use this flaw to bypass access restrictions…. Ubuntu Security Notice 1950-1 – It was discovered that Light Display Manager created .Xauthority files with incorrect permissions. A local attacker could use this flaw to bypass access restrictions.

Read more http://packetstormsecurity.com/files/123218/USN-1950-1.txt