Mozilla Firefox before 34.0 and SeaMonkey before 2.31 provide stylesheets with an incorrect primary namespace, which allows remote attackers to bypass intended access restrictions via an XBL binding.
http://www.mozilla.org/security/announce/2014/mfsa2014-84.html
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html