Firefox 3.5 has a critical JavaScript vulnerability

firefox-3.5If you are using Mozilla’s latest browser, Firefox 3.5 then you may be running in risk. There seems to be a critical JavaScript vulnerability in the newly launched 3.5 version of Firefox. Mozilla’s security blog has just published this post describing the vulnerability.

The vulnerability can be exploited by an attacker who tricks a victim into viewing a malicious Web page containing the exploit code. You may want to disable javascript’s JIT option till the Firefox team come up with the security patch release. To disable JIT follow these steps:

1. Enter about:config in the browser’s location bar.
2. Type jit in the Filter box at the top of the config editor.
3. Double-click the line containing javascript.options.jit.content setting the value to false.

Disabling the just in time compiler of javascript can reduce the performance of the javascript heavy webpage. But atleast it will save you till the security update comes. You can enable the JIT option again by following the above steps and changing value of javascript.options.jit.content to true.



5 Comments

  • Brian Jørgensen 16 July, 2009, 5:44

    How will this effect the users of Firefox 3.5, including me?

  • Viral Patel 16 July, 2009, 11:36

    Hey Brian… This will not at all effect the users of Firefox.. Firefox remains the user choice browser. The mozilla team will be working on the patch. I am also using Firefox.

  • Kumarasamy 16 July, 2009, 12:06

    Hey, I hope it’s happening for all the entries in about:config, that’s happening only when you are doing double click on it. May be this is a feature from FF.

  • Roman 16 July, 2009, 14:29

    FF 3.5′s JIT seem to cause trouble in some areas in generally. There are several things you might HAVE to change to make your JS working in 3.5. This even affects bigger open source projects, which usually have pretty clean JS code. I decided to stay away from it for now and keep using 3.0.x.

  • Brian Jørgensen 16 July, 2009, 18:10

    Thanks for the answer, good to hear :o)

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