Sony confirms The Last of Us 2 spoilers weren't published by a Naughty Dog employee. Someone from outside Naughty Dog got access to the files and published them online, and Sony knows who did it.
The rumors and reports are all wrong. The urban legend around The Last of Us 2's spoiler motivations goes a little something like this: Naughty Dog withheld a developer's pay, so the dev took revenge by leaking the game's most controversial cinematic sequences online for all to see. This rumor was predicated strongly on Naughty Dog's intense crunch culture, which apparently sees employees being hospitalized from mental breakdowns and overwork.
Sony recently set the record straight and confirmed the allegations are untrue. Sony tells GamesIndustry.biz that it has identified the perpetrator behind the leaks, but hasn't said whether or not it was a hacker, which is the most logical conclusion if the leaks weren't an inside job.
The leaks have had a tremendously disparaging effect on The Last of Us 2, Sony, and Naughty Dog. The controversial footage has been passed around and kicked off a wave of backlash in gaming communities, and Naughty Dog's own internal dev teams are devastated their hard work has been laid bare before it was ready.
Sony has since accelerated The Last of Us 2's release date next month to June in an effort to combat the leaks and stave off some of the negative pushback.