In an Irish court on Thursday, a FBI agent admitted publicly for the first time that the agency had control of a Tor hidden service operator’s company, Freedom Hosting, for a period of time. It had been widely suspected that the FBI or another American law enforcement agency used a particular Tor exploit to gain control.

Eric Eoin Marques, a dual Irish-American citizen, is currently facing extradition from Ireland to the United States on four charges of child pornography. (On Thursday, the Irish judge in the case allowed Marques to file for a new bail motion.) Marques is accused of running Freedom Hosting, a major hidden services provider on the Tor network that was notorious for hosting child porn sites.

According to the Irish Independent, “Investigators claimed that after his initial arrest at the end of July Marques managed to get back on the server—which had been taken over by the FBI—and change the passwords.”

As Ars reported previously, security researchers found malicious JavaScript embedded in Freedom Hosting pages. The attack code sent the compromised information back to a server in Virginia.

"Because this payload does not download or execute any secondary backdoor or commands it's very likely that this is being operated by an LEA [law-enforcement agent] and not by blackhats," independent researcher Vlad Tsrklevich wrote on his own website last month.