http://www.theregister.co.uk/2016/10/25/judge_orders_fbi_to_reveal_whether_exploits_were_okayed_by_white_house/
"The case is one of several the Feds are pursuing against more than 100 alleged users of the child sex abuse material exchange network called the Playpen. The prosecutions have become test grounds over investigators' use of hacking tools to unmask Tor users – Playpen was hidden in the Tor network and agents injected tracking software into Playpen visitors' browsers to identify users.
...
The Playpen investigation also sparked last year's controversy over Carnegie-Mellon University's part. It was accused of revealing de-anonymisation research to the FBI in 2014, and last November said it wasn't paid for the research, but rather, served with a subpoena."