He really did that? Jeez, you're right. Still, such attacks have doubtless been used before. Even if they haven't broken the core protocol, I'd assume they've got a few zero-days sitting around.
> News reports linked a Firefox browser vulnerability to a United States Federal Bureau of Investigation (FBI) operation targeting Freedom Hosting's owner, Eric Eoin Marques. In August 2013, it was discovered that the Firefox browsers in many older versions of the Tor Browser Bundle were vulnerable to a JavaScript attack, as NoScript was not enabled by default. This attack was being exploited to send users' MAC and IP addresses and Windows computer names to the attackers. The FBI acknowledged they were responsible for the attack in a September 12, 2013 court filing in Dublin