firefox / thunderbird is vulnerable to arbitrary code execution. A web page containing malicious content could cause Firefox to crash or, potentially, execute arbitrary code with the privileges of the user running Firefox.
secunia.com/advisories/48920
secunia.com/advisories/48922
secunia.com/advisories/48972
secunia.com/advisories/49047
secunia.com/advisories/49055
www.debian.org/security/2012/dsa-2457
www.debian.org/security/2012/dsa-2458
www.debian.org/security/2012/dsa-2464
www.mandriva.com/security/advisories?name=MDVSA-2012:066
www.mandriva.com/security/advisories?name=MDVSA-2012:081
www.mozilla.org/security/announce/2012/mfsa2012-20.html
www.mozilla.org/security/known-vulnerabilities/firefoxESR.html
www.securityfocus.com/bid/53223
access.redhat.com/errata/RHSA-2012:0515
access.redhat.com/security/updates/classification/#critical
bugzilla.mozilla.org/show_bug.cgi?id=680456
bugzilla.mozilla.org/show_bug.cgi?id=706381
bugzilla.mozilla.org/show_bug.cgi?id=708825
bugzilla.mozilla.org/show_bug.cgi?id=714614
bugzilla.mozilla.org/show_bug.cgi?id=716556
bugzilla.mozilla.org/show_bug.cgi?id=720305
bugzilla.mozilla.org/show_bug.cgi?id=723453
bugzilla.mozilla.org/show_bug.cgi?id=726332
bugzilla.mozilla.org/show_bug.cgi?id=726502
bugzilla.mozilla.org/show_bug.cgi?id=732941
bugzilla.mozilla.org/show_bug.cgi?id=732951
bugzilla.mozilla.org/show_bug.cgi?id=733282
bugzilla.mozilla.org/show_bug.cgi?id=733979
bugzilla.mozilla.org/show_bug.cgi?id=735073
bugzilla.mozilla.org/show_bug.cgi?id=735943
bugzilla.mozilla.org/show_bug.cgi?id=736589
bugzilla.mozilla.org/show_bug.cgi?id=736609
bugzilla.mozilla.org/show_bug.cgi?id=737129
bugzilla.mozilla.org/show_bug.cgi?id=737182
bugzilla.mozilla.org/show_bug.cgi?id=737384
bugzilla.mozilla.org/show_bug.cgi?id=737875
bugzilla.mozilla.org/show_bug.cgi?id=740595
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A17074