"Mozilla is scrambling to patch a vulnerability in Firefox that is apparently being exploited in the wild to unmask Tor Browser users.
Earlier today, a small package of SVG, JavaScript and x86 code popped up on a Tor mailing list that, when opened by Firefox or Tor Browser on a Windows PC, phones home to a remote server and leaks the user's MAC address, hostname and potentially their public IP address. Typically, this exploit would be embedded in a webpage and leap into action when opened by an unsuspecting visitor."
http://www.theregister.co.uk/2016/11/30/possible_tor_browser_decloak_zero_day_dropped_patch_in_works/
https://web.archive.org/web/20161130072235/http://www.theregister.co.uk/2016/11/30/possible_tor_browser_decloak_zero_day_dropped_patch_in_works/
The malicious payload it delivers, according to an independent researcher who goes by the Twitter handle @TheWack0lian, is almost identical to one that was used in 2013 to deanonymize people visiting a Tor-shielded child pornography site. The FBI ultimately acknowledged responsibility for the exploit, which was embedded in Web pages served by a service known as Freedom Hosting.
http://arstechnica.com/security/2016/11/firefox-0day-used-against-tor-users-almost-identical-to-one-fbi-used-in-2013/
https://web.archive.org/web/20161130031656/http://arstechnica.com/security/2016/11/firefox-0day-used-against-tor-users-almost-identical-to-one-fbi-used-in-2013/
"This is an Javascript exploit actively used against TorBrowser NOW. It consists of one HTML and one CSS file, both pasted below and also de-obscured. The exact functionality is unknown but it's getting access to "VirtualAlloc" in "kernel32.dll" and goes from there. Please fix ASAP."
https://lists.torproject.org/pipermail/tor-talk/2016-November/042639.html
https://web.archive.org/web/20161130003501/https://lists.torproject.org/pipermail/tor-talk/2016-November/042639.html
[Editor's Note: The reporting only mentions Windows PCs, but it might not be limited to this OS.]
(Score: 0) by Anonymous Coward on Thursday December 01 2016, @11:23AM
It's implemented in Wine: https://source.winehq.org/WineAPI/VirtualAlloc.html [winehq.org]