SLiM Simple Login Manager 1.3.0 places the X authority magic cookie (mcookie) on the command line when invoking xauth from (1) app.cpp and (2) switchuser.cpp, which allows local users to access the X session by listing the process and its arguments.
https://www.redhat.com/archives/fedora-package-announce/2010-January/msg00009.html
https://www.redhat.com/archives/fedora-package-announce/2010-January/msg00000.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/50611
http://www.securityfocus.com/bid/35015
http://www.openwall.com/lists/oss-security/2009/05/18/2
http://secunia.com/advisories/38070