As the most closely related thread currently open, it seems appropriate to suggest that ANYONE USING FIREFOX should visit the thread: Tech: FIREFOX USERS CRITICAL ALERT.
Within the past few days, Mozilla/Firefox have issued warnings about vulnerabilities found in Firefox. The code for exploiting them has been published on the web. Partial fixes are available, and more will come.
Firefox users may have missed the three other security fixes issued recently, and may need to look for updates. This new one is the first Firefox vulnerability to receive an "extremely critical" rating from the AV guys, and you need to pay attention.