Firefox exploit targets zero day vulns

Warning as malicious script goes feral

By John Leyden • Get more from this author

Posted in Enterprise Security, 9th May 2005 11:38 GMT

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Security researchers have discovered two unpatched vulnerabilities in Firefox, the popular alternative web browser. The security bugs affect even the latest version of Firefox (version 1.0.3) and create a means for attackers to seize control of vulnerable systems using cross-site scripting attacks.

One vulnerability enables arbitrary JavaScript code with escalated privileges to be executed via a specially crafted JavaScript URL. Successful exploitation requires that a site is allowed to install software (default sites are "update.mozilla.org" and "addons.mozilla.org"). This would normally drastically reduce the scope for mischief - but for a second security bug, involving "IFRAME" JavaScript URLs, which creates a means to execute arbitrary HTML and script code in the context of an arbitrary site.

A combination of the two vulnerabilities can be exploited to execute arbitrary code on vulnerable systems, according to Danish security firm Secunia. Exploit code is publicly available greatly increasing the chance of attack, it warns. The vulnerabilities - described by Secunia as "extremely critical" - have been confirmed in version 1.0.3 of Firefox. Other versions may also be affected.

Users are advised to disable JavaScript and the software installation option within Firefox pending a more comprehensive fix from the Mozilla Foundation. ®