As far as I am concerned the origin of the leaked video is a link in the source code of the cbs homepage.
Some people claim this was a mistake like forgetting to lock the door but let me get this straight for everyone who may not be familiar with how "computerish" things work.

THIS DOESNT MAKE ANY SENSE.  A LINK DIRECTING YOU TO A PLAYER HOST THAT STREAMS THE  EPISODE HAS NOTHING TO DO HIDING BETWEEN SOURCES AND COMPUTER CODES NOT EVEN IF SOMEBODY FUCKED THINGS UP BEYOND IMAGINATION. IT IS TECHNICALLY JUST NOT POSSIBLE:

Saying this episode was leaked due to a terrible mistake is like saying is was leaked because the monkey didnt war a blue hat.

The only reason for this link to be in a sorce code is because somebody put it there on purpose.