Tor Project Director accused the FBI of paying Carnegie Mellon University $1 million to disclose technique they had discovered to unmask Tor users and reveal their IP addresses. Federal Bureau of Investigation has denied the claims. FBI spokeswoman said the allegation that we paid [CMU] $1 Million to hack into Tor is inaccurate. Tor Project team discovered more than hundred new Tor relays that modified Tor protocol headers to track online people who were looking for Hidden Services. One such IP address belongs to alleged Silk Road 2 lieutenant who was arrested in January 2014.
Source: https://thehackernews.com/2015/11/fbi-unmask-tor.html