pkexec.c in pkexec in libpolkit in PolicyKit 0.96 allows local users to determine the existence of arbitrary files via the argument.
https://exchange.xforce.ibmcloud.com/vulnerabilities/57543
http://security.gentoo.org/glsa/glsa-201204-06.xml
http://secunia.com/advisories/48817
http://secunia.com/advisories/39149