If you use Firefox, it’s time to update your browser.
The exploit, which a user discovered on Aug. 5 and brought to Mozilla’s attention, takes advantage of a vulnerability in Firefox’s PDF viewer.
The exploit was found in an advertisement on a Russian news outlet’s website, but it could be running elsewhere across the Web as well. Veditz said the code search for files that were “surprisingly developer focused.”
The Firefox mobile browser for Android was also unaffected because it does not use the Firefox PDF viewer.
Firefox has already issued an update to address the exploit. Users are urged to update to Firefox 39.0.3 to plug the potential security gap.