Four preview episodes were leaked during Game of Thrones' fifth season and the fourth episode of season seven found its way out from the show's Indian distributor.
Already the most pirated show in TV history, the hit fantasy drama has been plagued by leaks in recent weeks following the premiere of the penultimate seventh season.
Prime Focus Technology is responsible for storing and processing episodes of Game of Thrones for the video-streaming app Hotstar, which is a subsidiary of the local broadcaster Star India, local media said.
"The error appears to have originated with a third party vendor and the episode was removed as soon as it was recognised", it added.
But an official subsidiary of HBO themselves leaking an episode is certainly new.
The network confirmed that they recently experienced a cyber incident, which resulted in the compromise of proprietary information, reports E!
Screen shots and clips from the episode began circulating online early Wednesday morning, while the full episode was uploaded to various torrent websites.
As it relates to the latest leak of HBO's highest-profile series, the premium cabler's worldwide partners have goofed like this before: During last year's season six run, an episode leaked ahead of its premiere date after it was accidentally made available on HBO Nordic.
At the end of July HBO was hacked and 1.5TB of data stolen. However, only episodes of other HBO series, including Insecure and Ballers have been illegally shared so far.