Mozilla Firefox before 47.0 allows remote attackers to discover the list of disabled plugins via a fingerprinting attack involving Cascading Style Sheets (CSS) pseudo-classes.
https://bugzilla.mozilla.org/show_bug.cgi?id=1025267
http://www.ubuntu.com/usn/USN-2993-1
http://www.securitytracker.com/id/1036057
http://www.mozilla.org/security/announce/2016/mfsa2016-59.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00016.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00014.html