[Au Jus Demon]

Valve accidentally exposed stuff through the Steam API that shouldn't have been public, and it ended up leaking the titles of a bunch of unreleased and unannounced games along with their full achievement lists.

Persona 6 is probably the biggest example. Pretty much the entire achievement list leaked, and a lot of it spoils locations, game mechanics, characters, and story elements.

Pretty big fuck up by Valve.