Sometimes, rumors are incorrect, and other times, they've proven to be true. When it comes to the rumblings of the existence of a Grand Theft Auto trilogy remaster, it appears that it was the latter, in this case. The South Korean Game Rating and Administration Committee has let another game slip prior to its official announcement: Grand Theft Auto: The Trilogy - The Definitive Edition. The game, which would likely be a collection of Grand Theft Auto 3, Vice City, and San Andreas, was given a classification earlier today, with franchise publisher Take Two Interactive having filed for the rating. No platforms or release window was listed, though we can likely expect to see an official announcement follow soon.

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[James_]

Since nothing's been released yet, I have to ask what game launcher were those found in?

The Rockstar Games launcher, unsurprisingly.

An absolute truck ton of achievement icons were also leaked too, some achievements slightly changed and some even new. Meaning there's probably gonna be at least some form of new content.
I would post them here but that would take ages, so I'll just link to GTAForums where the icons were found.