PolicyKit 0.103 sets the AdminIdentities to "wheel" by default, which allows local users in the wheel group to gain root privileges without authentication.
https://launchpad.net/ubuntu/+source/policykit-1/0.103-1
https://bugs.gentoo.org/show_bug.cgi?id=401513
http://www.openwall.com/lists/oss-security/2012/03/28/2
http://www.openwall.com/lists/oss-security/2012/03/28/1
http://www.mail-archive.com/polkit-devel%40lists.freedesktop.org/msg00327.html
http://security.gentoo.org/glsa/glsa-201204-06.xml
http://secunia.com/advisories/48817
http://cgit.freedesktop.org/PolicyKit/commit/?id=763faf434b445c20ae9529100d3ef5290976d0c9