Mozilla Firefox before 31.0 does not properly restrict use of drag-and-drop events to spoof customization events, which allows remote attackers to alter the placement of UI icons via crafted JavaScript code that is encountered during (1) page, (2) panel, or (3) toolbar customization.
https://security.gentoo.org/glsa/201504-01
https://bugzilla.mozilla.org/show_bug.cgi?id=910375
https://bugzilla.mozilla.org/show_bug.cgi?id=1000514
http://www.securitytracker.com/id/1030619
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
http://www.mozilla.org/security/announce/2014/mfsa2014-60.html