An incident like this underscores both how many people are looking to get a peek at Game of Thrones episodes before they release and how hard it is for HBO to make sure its bases are covered, especially when third parties are part of the mix.

"Yes, we hacked HBO and 1.5 TB of sensitive data and films is in our hands!" The "Game of Thrones" script for the now-leaked episode and two unreleased episodes of other HBO shows were leaked from that hack. Someone at distribution partner Star India is thought to be responsible for the episode's "early" airing.

A watermark on the episode (see above), suggests the screener was intended for internal use at HBO. In a statement, the company said it is taking the leak "very seriously and have immediately initiated forensic investigations".

Star World Premiere telecasts censored episodes of Game of Thrones on Tuesday nights, while uncensored episodes are put up on Hotstar the prior morning.

HBO has been trying to plug up leak after leak surrounding Game of Thrones this season, but the latest leak is the most dramatic. Furthermore, the episode length lines up with the scheduled run time of the fourth episode that appears on HBO's website. Now the network is working along with law enforcement and independent cyber security experts to investigate the attack. HBO has yet to issue an official response to this leak.

A coordinated cyberattack on July 27 saw hackers walk away with one-and-a-half terabytes of HBO data, a publication reported, which included video footage, internal documents and email correspondence. It is unclear how the episodes were leaked.

Some journalists received emails last Sunday night, written in somewhat halting English, announcing "the greatest leak of cyber space era is happening" and urging the media to spread the word.