The problem is in the Just-In-Time (JIT) Javascript compiler. Experts said that it can be used by some malicious guys to execute malicious codes at the internet users’ computers.

For example: If you are using Firefox 3.5 or the previous versions in viewing a website that contains malicious codes which is making use of this vulnerability, the code will be automatically activated.

So, to avoid such attack while the Firefox update is not yet released, you need to temporarily disable the JIT by typing in the location bar this: about:config then type jit in the Filter box at the top of the config editor the next double-click the line containing javascript.options.jit.content setting the value to false.

Now, since it’s a temporary remedy, once your Firefox has been updated already, reverse the above procedure for your Firefox browser to function fully. Here’s what to do: about:config then type jit in the Filter box at the top of the config editor the next double-click the line containing javascript.options.jit.content setting the value to true.