The file-download dialog in Mozilla Firefox before 44.0 on OS X enables a certain button too quickly, which allows remote attackers to conduct clickjacking attacks via a crafted web site that triggers a single-click action in a situation where a double-click action was intended.
https://security.gentoo.org/glsa/201605-06
https://bugzilla.mozilla.org/show_bug.cgi?id=1116385
http://www.securitytracker.com/id/1034825
http://www.mozilla.org/security/announce/2016/mfsa2016-08.html