Not everything is safe on the onion router.
The Register explains:
The FBI’s preferred tool for unmasking Tor users has brought about another arrest: a suspected sextortionist who allegedly tricked young girls into sharing nude pics of themselves and then blackmailed his victims.
As we learned from previous investigations, the Feds have a network investigative technique (NIT) up their sleeve that can potentially identify folks using the anonymizing system Tor.
The NIT involves a specially crafted video file – such as this one – that when downloaded and opened causes the media player to ping an FBI-controlled server somewhere on the internet. If this happens, and if the surreptitious connection does not go through the Tor network, it will leak the public IP address of the user to the Feds. This information can be used to identify the person's ISP and, with a subpoena, the subscriber's identity, leading to their arrest.