The navigator.sendBeacon implementation in Mozilla Firefox before 37.0, Firefox ESR 31.x before 31.6, and Thunderbird before 31.6 processes HTTP 30x status codes for redirects after a preflight request has occurred, which allows remote attackers to bypass intended CORS access-control checks and conduct cross-site request forgery (CSRF) attacks via a crafted web site, a similar issue to CVE-2014-8638.
https://security.gentoo.org/glsa/201512-10
https://bugzilla.mozilla.org/show_bug.cgi?id=1111834
http://www.ubuntu.com/usn/USN-2552-1
http://www.ubuntu.com/usn/USN-2550-1
http://www.securitytracker.com/id/1032000
http://www.securitytracker.com/id/1031996
http://www.securityfocus.com/bid/73457
http://www.oracle.com/technetwork/topics/security/bulletinapr2015-2511959.html
http://www.mozilla.org/security/announce/2015/mfsa2015-37.html
http://www.debian.org/security/2015/dsa-3212
http://www.debian.org/security/2015/dsa-3211
http://rhn.redhat.com/errata/RHSA-2015-0771.html
http://rhn.redhat.com/errata/RHSA-2015-0766.html
http://lists.opensuse.org/opensuse-security-announce/2015-07/msg00031.html
http://lists.opensuse.org/opensuse-security-announce/2015-05/msg00012.html
http://lists.opensuse.org/opensuse-security-announce/2015-04/msg00006.html
http://lists.opensuse.org/opensuse-security-announce/2015-04/msg00003.html