The leak follows the release of several scripts of episodes onto the internet due to a security breech on a server in the BBC Worldwide office in Miami. Although video material was accessible on the servers it was originally thought that no material had been accessed. It is now believed the leaked episode comes from the same source. Although complete in duration, the episode in question lacks several effects shots and has a place holder title sequence.
A BBC spokesperson told RadioTimes.com
This is part of BBC Worldwide's ongoing security investigation into leaked unfinished Doctor Who materials. This content is currently being removed and originates from the same Miami server disabled last week, it is not a new issue. We'd like to thank the amazing Doctor Who fans who are continuing to keep fansites and social media spoiler-free.Showrunner Steven Moffat was asked about the script leak at the London Film & Comic Con on Saturday where he described the leak as horrible, miserable and upsetting for Doctor Who team.