CVE 2012-4205
Mozilla Firefox before 17.0, Thunderbird before 17.0, and SeaMonkey before 2.14 assign the system principal, rather than the sandbox principal, to XMLHttpRequest objects created in sandboxes, which allows remote attackers to conduct cross-site request forgery (CSRF) attacks or obtain sensitive information by leveraging a sandboxed add-on.
See the 
CVE page on Mitre.org
for more details.
