Microsoft’s Edge extensions store appears to be hosting illegal copies of a number of iconic games, including Mario Kart 64, Super Mario Bros., Sonic the Hedgehog 2, Pac-Man, Tetris, Cut The Rope, and even Microsoft’s own smash hit Minecraft. The developers listed on the titles aren’t Microsoft, Nintendo, or any other recognizable game developer, meaning that they almost certainly aren’t official copies of the games.

We found 35 listings across 10 different “developers” with names like “GamePro Inc,” “Gamelands,” “StayReal” and “Kday,” including a number of duplicate games. Many listings, even from different developers, had very similar descriptions, indicating that they could be coming from the same source.

Here are screenshots of just a few of the games we found:

Oddly, Microsoft itself appeared to promote the browser extensions in what looks to be a now-deleted tweet from the @MSEdgeDev account, which we saw via ResetEra.

Image: KoolAid on ResetEra

We didn’t see this purported tweet ourselves, and it isn’t currently on the @MSEdgeDev account right now. But one brave soul on Twitter, Jordan Chase, said he installed the Mario Kart 64 extension on Twitter — and he said that in a reply to a now-deleted tweet from @MSEdgeDev.

In his tweet, Chase said the Mario Kart 64 extension downloads a ROM of the game. While emulators are generally legal, and some sites (like Internet Archive) host abandonware you can play in a browser, it’s extremely unlikely that Nintendo, which is well-known for cracking down on sites hosting ROMs and pirated content, would let people download copies of its most-loved games over free browser extensions.

The Tetris extension also appears to be a clone of the famous puzzle game, though it didn’t download a ROM, according to Chase. He also said he installed the Pac-Man extension, and it “seems like it’s using direct assets from the original game.” I didn’t install the games myself in case they were doing something nefarious, and I’d recommend against putting them on your machine.

Some of the games we found have reviews dating back to October, indicating they have been sitting unnoticed in Microsoft’s catalog for quite some time. It’s unclear why they have been available for so long.

Many listings attempt to skirt trouble with dubious disclaimers acknowledging the listings aren’t affiliated with the original games. Here’s one for the listing for Mario Kart 64, for example:

IMPORTANT: This emulator is not affiliated with nor endorsed by Nintendo. All graphics, games, and other multimedia are copyrighted to their respective owners and authors. This game is for ALL Mario fans!

Microsoft and Nintendo tell The Verge they are looking into the situation.