CVE 2010-0179
Mozilla Firefox before 3.0.19 and 3.5.x before 3.5.8, and SeaMonkey before 2.0.3, when the XMLHttpRequestSpy module in the Firebug add-on is used, does not properly handle interaction between the XMLHttpRequestSpy object and chrome privileged objects, which allows remote attackers to execute arbitrary JavaScript via a crafted HTTP response.
See the 
CVE page on Mitre.org
for more details.
