The favicon functionality in Firefox before 1.0.3 and Mozilla Suite before 1.7.7 allows remote attackers to execute arbitrary code via a <LINK rel="icon"> tag with a javascript: URL in the href attribute, aka "Firelinking."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10655
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A100021
https://bugzilla.mozilla.org/show_bug.cgi?id=290036
http://www.securityfocus.com/bid/15495
http://www.securityfocus.com/bid/13216
http://www.redhat.com/support/errata/RHSA-2005-386.html
http://www.redhat.com/support/errata/RHSA-2005-384.html
http://www.redhat.com/support/errata/RHSA-2005-383.html
http://www.mozilla.org/security/announce/mfsa2005-37.html
http://www.kb.cert.org/vuls/id/973309
http://www.gentoo.org/security/en/glsa/glsa-200504-18.xml