CVE 2009-3988
Mozilla Firefox 3.0.x before 3.0.18 and 3.5.x before 3.5.8, and SeaMonkey before 2.0.3, does not properly restrict read access to object properties in showModalDialog, which allows remote attackers to bypass the Same Origin Policy and conduct cross-site scripting (XSS) attacks via crafted dialogArguments values.
See the 
CVE page on Mitre.org
for more details.
