Developers with both Mozilla and Tor have published browser updates that patch a critical Firefox vulnerability being actively exploited to deanonymize people using the privacy service.
“The security flaw responsible for this urgent release is already actively exploited on Windows systems,” a Tor official wrote in an advisory published Wednesday afternoon. “Even though there is currently, to the best of our knowledge, no similar exploit for OS X or Linux users available, the underlying bug affects those platforms as well. Thus we strongly recommend that all users apply the update to their Tor Browser immediately.”
The Tor browser is based on the open-source Firefox browser developed by the Mozilla Foundation. Shortly after this post went live, Mozilla security official Daniel Veditz published a blog post that said the vulnerability has also been fixed in a just-released version of Firefox for mainstream users. On early Wednesday, Veditz said, his team received a copy of the attack code that exploited a previously unknown vulnerability in Firefox.