Firefox 3.5.1 Released: Highly Critical Update Fixes Security Hole

A critical JavaScript vulnerability has been found in Firefox 3.5, which was released less than a month ago. The security hole can be exploited by any attacker to trick users into viewing malicious web pages by disabling the Just-in-time (JIT) JavaScript compiler.

This JIT compiler has been introduced in Firefox 3.5 as part of it’s new JavaScript engine TraceMonkey.

Apart from this “highly” critical update, several stability issues such as crashing when visiting some websites on the sparc platform and also a slow startup issue on some Windows systems have been fixed. Firefox 3.5 took quite a long time to load on some Windows PCs, due to accessing Internet Explorer’s Temporary Internet Files and the Windows Temp folder.

If you have Firefox 3.5 already installed, then you should have already received the fixes through Automatic Updates. You can check if Firefox has been updated through Help –> Check for Updates. In case Automatic Updates has been turned off, Firefox will show availability of the critical update as shown in image below.