Gentoo has issued updates for mozilla-firefox, mozilla-firefox-bin, seamonkey, seamonkey-bin, mozilla-thunderbird, mozilla-thunderbird-bin, and xulrunner. These fix some weaknesses and vulnerabilities, which can be exploited by malicious people to disclose sensitive information, conduct cross-site scripting attacks, bypass certain security restrictions, conduct spoofing attacks, or to compromise a user's system.

For more information:
SA28758
SA29133
SA29526
SA29787

Solution
Update to a fixed version.
Further details available to Secunia VIM customers

Other references
Further details available to Secunia VIM customers

Deep Links
Links available to Secunia VIM customers