dmrc.c in Light Display Manager (aka LightDM) before 1.1.1 allows local users to read arbitrary files via a symlink attack on ~/.dmrc.
https://bugs.launchpad.net/ubuntu/%2Bsource/lightdm/%2Bbug/883865
http://www.ubuntu.com/usn/USN-1262-1
http://bazaar.launchpad.net/~lightdm-team/lightdm/trunk/revision/1299