The nsExternalAppHandler::SetUpTempFile function in Mozilla Firefox 1.5.0.9 creates temporary files with predictable filenames based on creation time, which allows remote attackers to execute arbitrary web script or HTML via a crafted XMLHttpRequest.
http://www.securityfocus.com/archive/1/459163/100/0/threaded
http://www.securityfocus.com/archive/1/459162/100/0/threaded
http://www.gentoo.org/security/en/glsa/glsa-200703-08.xml
http://security.gentoo.org/glsa/glsa-200703-04.xml