Mozilla Firefox before 28.0, Firefox ESR 24.x before 24.4, Thunderbird before 24.4, and SeaMonkey before 2.25 might allow local users to gain privileges by modifying the extracted Mar contents during an update.
https://security.gentoo.org/glsa/201504-01
http://www.oracle.com/technetwork/topics/security/bulletinapr2016-2952098.html
http://www.mozilla.org/security/announce/2014/mfsa2014-16.html
http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00016.html