Mozilla Firefox before 2.0.0.15 and SeaMonkey before 1.1.10 do not properly implement JAR signing, which allows remote attackers to execute arbitrary code via (1) injection of JavaScript into documents within a JAR archive or (2) a JAR archive that uses relative URLs to JavaScript files.

More... (http://nvd.nist.gov/nvd.cfm?cvename=CVE-2008-2801)