It would appear that running any of 600 add-ons in Mozilla Firefox opens up a terrible hole. When exploited, this hole allows a hacker to steal "session information, including session cookies and session history". Mozilla promises a fix by February 5th, with the release of Firefox version 2.0.0.12. While Mozilla classifies this threat as a "high risk", there is some controversy in the hacker world as to how bad this threat really is. According to a hacker, via "hiredhacker.com", this isn't as big a problem as people have made it out to be. However, it is certainly more serious than "leaking a few variables", and should definitely be patched as soon as possible.