Mozilla officials say they’ll release a Firefox update on Tuesday that fixes the same cross-platform, malicious code-execution vulnerability patched Friday in the Tor browser.
The vulnerability allows an attacker who has a man-in-the-middle position and is able to obtain a forged certificate to impersonate Mozilla servers, Tor officials warned in an advisory. From there, the attacker could deliver a malicious update for NoScript or many other Firefox extensions installed on a targeted computer. The fraudulent certificate would have to be issued by any one of several hundred Firefox-trusted certificate authorities (CA).
While it probably would be challenging to hack a CA or trick one into issuing the necessary certificate for addons.mozilla.org, such a capability is well within reach of nation-sponsored attackers, who are precisely the sort of adversaries included in the Tor threat model. In 2011, for instance, hackers tied to Iran compromised Dutch CA DigiNotar and minted counterfeit certificates for more than 200 addresses, including Gmail and the Mozilla addons subdomain.
Update early and often
Friday’s advisory from Tor urges users to install the update as soon as possible. Shortly after this post went live, Mozilla officials said they planned to followed suit on Tuesday. According to a report posted Thursday by researcher Ryan Duff, production versions of Firefox are susceptible, although a nightly build version released on September 4 is not susceptible.
