Mozilla Firefox before 3.0.11, Thunderbird before 2.0.0.22, and SeaMonkey before 1.1.17 use the HTTP Host header to determine the context of a document provided in a non-200 CONNECT response from a proxy server, which allows man-in-the-middle attackers to execute arbitrary web script by modifying this CONNECT response, aka an "SSL tampering" attack.
http://research.microsoft.com/apps/pubs/default.aspx?id=79323
http://research.microsoft.com/pubs/79323/pbp-final-with-update.pdf
https://bugzilla.mozilla.org/show_bug.cgi?id=479880
https://bugzilla.redhat.com/show_bug.cgi?id=503578
http://secunia.com/advisories/35331
http://secunia.com/advisories/35415
http://secunia.com/advisories/35431
http://secunia.com/advisories/35439
http://secunia.com/advisories/35440
http://secunia.com/advisories/35468
http://secunia.com/advisories/35536
http://secunia.com/advisories/35561
http://secunia.com/advisories/35602
http://secunia.com/advisories/35882
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11764
https://rhn.redhat.com/errata/RHSA-2009-1095.html
http://sunsolve.sun.com/search/document.do?assetkey=1-66-264308-1
https://www.redhat.com/archives/fedora-package-announce/2009-July/msg00444.html
https://www.redhat.com/archives/fedora-package-announce/2009-July/msg00504.html
https://www.redhat.com/archives/fedora-package-announce/2009-June/msg00574.html
https://www.redhat.com/archives/fedora-package-announce/2009-June/msg00657.html
http://www.debian.org/security/2009/dsa-1820
http://www.debian.org/security/2009/dsa-1830
http://www.mandriva.com/security/advisories?name=MDVSA-2009:141
http://www.mozilla.org/security/announce/2009/mfsa2009-27.html
http://www.redhat.com/support/errata/RHSA-2009-1126.html
http://www.securitytracker.com/id?1022396