CVE 2010-1585

The nsIScriptableUnescapeHTML.parseFragment method in the ParanoidFragmentSink protection mechanism in Mozilla Firefox before 3.5.17 and 3.6.x before 3.6.14, Thunderbird before 3.1.8, and SeaMonkey before 2.0.12 does not properly sanitize HTML in a chrome document, which makes it easier for remote attackers to execute arbitrary JavaScript with chrome privileges via a javascript: URI in input to an extension, as demonstrated by a javascript:alert sequence in (1) the HREF attribute of an A element or (2) the ACTION attribute of a FORM element.

See the CVE page on Mitre.org for more details.