Game of Thrones' upcoming episode, The Door, leaked to several torrent and pirating sites last night, a full day before its HBO premiere. The source of the leak appears to be HBO itself. As TorrentFreak points out, Episode 5, Season 6 was available to view last night on HBO Nordic, available in Sweden, Denmark, Norway, and Finland.

TorrentFreak managed to get a screencap of the show on HBO Nordic:

Game of Thrones was the most pirated TV show of 2015 and 2014, something HBO has tried to combat by offering viewers a simultaneous premiere in 170 countries, and getting rid of advance press screeners. HBO Now also seemed like a compromise to potential pirates who didn't want to sign up for cable. But sometimes you just can't prevent a leak.

The episode has since been removed from HBO Nordic's website, but it appeared to have been up for several hours — more than enough time for it to make the internet rounds.