firefox is vulnerable to information disclosure. The vulnerability exists in the way Thunderbird handled error responses returned from proxy servers. If an attacker is able to conduct a man-in-the-middle attack against a Thunderbird instance that is using a proxy server, they may be able to steal sensitive information from the site Thunderbird is displaying.
osvdb.org/55160
research.microsoft.com/apps/pubs/default.aspx?id=79323
research.microsoft.com/pubs/79323/pbp-final-with-update.pdf
secunia.com/advisories/35331
secunia.com/advisories/35415
secunia.com/advisories/35431
secunia.com/advisories/35439
secunia.com/advisories/35440
secunia.com/advisories/35468
secunia.com/advisories/35536
secunia.com/advisories/35561
secunia.com/advisories/35602
secunia.com/advisories/35882
slackware.com/security/viewer.php?l=slackware-security&y=2009&m=slackware-security.372468
slackware.com/security/viewer.php?l=slackware-security&y=2009&m=slackware-security.425408
sunsolve.sun.com/search/document.do?assetkey=1-66-264308-1
www.debian.org/security/2009/dsa-1820
www.debian.org/security/2009/dsa-1830
www.mandriva.com/security/advisories?name=MDVSA-2009:141
www.mozilla.org/security/announce/2009/mfsa2009-27.html
www.redhat.com/security/updates/classification/#moderate
www.redhat.com/support/errata/RHSA-2009-1126.html
www.securityfocus.com/bid/35326
www.securityfocus.com/bid/35380
www.securitytracker.com/id?1022396
www.slackware.com/security/viewer.php?l=slackware-security&y=2009&m=slackware-security.454275
www.ubuntu.com/usn/usn-782-1
www.vupen.com/english/advisories/2009/1572
access.redhat.com/errata/RHSA-2009:1126
bugzilla.mozilla.org/show_bug.cgi?id=479880
bugzilla.redhat.com/show_bug.cgi?id=503578
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11764
rhn.redhat.com/errata/RHSA-2009-1095.html
www.redhat.com/archives/fedora-package-announce/2009-July/msg00444.html
www.redhat.com/archives/fedora-package-announce/2009-July/msg00504.html
www.redhat.com/archives/fedora-package-announce/2009-June/msg00574.html
www.redhat.com/archives/fedora-package-announce/2009-June/msg00657.html