But don't get too excited. It's Smurfs 2.
First reported by Torrentfreak, this is pretty big news in the downloading-shit-without-paying-for-it community. 4K Blu-rays' AACS 2.0 encryption has survived decoding until now and was thought to be unbreakable. Hosted on private tracker website UltraHDClub, though — as well as UHDClub's competitor IPT — the Smurfs 2 torrent is being touted as the "first Ultra HD Blu-ray disc in (sic) the net!"
The 53.3GB download has been confirmed to be a full copy of the Smurfs 2 4K Blu-ray disc including the HDR encoding for the video file, which sets it apart from the swathe of 'HDR' rips out there — which are basically recordings of a screen playing back a 4K HDR movie, lacking the per-display luminance settings that set a proper HDR video file apart from the crowd.