A critical security vulnerability affecting the latest Firefox 3.5 release has been identified by Mozilla. This vulnerability is caused by the TraceMonkey Javascript engine and allows malicious websites to execute code in your PC.

To get protected from this vulnerability, disable the TraceMonkey optimizer by following these steps.

1. Type about:config into the Firefox address bar and hit enter.
2. Hit “I’ll be careful, I promise” button.
3. Type in “javascript.options.jit.content” into the Filter bar. Double click on it to change its value to False.

Doing this may affect the browsers performance on Javascript intensive websites like Gmail. However, it is advised to disable TraceMonkey until Mozilla releases a patch for this vulnerability.

[via]