Simple Desktop Display Manager (SDDM) before 0.10.0 allows local users to log in as user "sddm" without authentication.
https://github.com/sddm/sddm/wiki/0.10.0-Release-Announcement
https://github.com/sddm/sddm/pull/279/files
https://exchange.xforce.ibmcloud.com/vulnerabilities/98421
https://bugzilla.redhat.com/show_bug.cgi?id=1149608
http://www.securityfocus.com/bid/70767
http://www.openwall.com/lists/oss-security/2014/10/06/4
http://lists.fedoraproject.org/pipermail/package-announce/2014-October/141550.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-October/141494.html