Login Window in Apple OS X before 10.11.6 allows attackers to gain privileges via a crafted app that leverages a "type confusion."
https://support.apple.com/HT206903
http://www.securitytracker.com/id/1036348
http://www.securityfocus.com/bid/91824
http://lists.apple.com/archives/security-announce/2016/Jul/msg00000.html