The mozilla::a11y::HyperTextAccessible::GetChildOffset function in the accessibility implementation in Mozilla Firefox before 49.0 allows remote attackers to execute arbitrary code via a crafted web site.
https://security.gentoo.org/glsa/201701-15
https://bugzilla.mozilla.org/show_bug.cgi?id=1280387
http://www.securitytracker.com/id/1036852
http://www.securityfocus.com/bid/93052
http://www.mozilla.org/security/announce/2016/mfsa2016-85.html