https://minecraftcreepypasta.fandom.com/wiki/Entity_303

Entity 303 (nicknamed "303") is a creepypasta commonly said to be "the New Herobrine". According to the pasta, a former Mojang employee was fired by Notch (the creator of Minecraft). Now he wants revenge on Mojang and Minecraft players alike. Entity 303 is said to be not just the former employee but a whole team of hackers going by usernames like "303mojang.com303," and "entity.303". If you have any files on your computer that are named anything with "303", then it could be 303's hackers. 303 can also hack into players' worlds and corrupt them. 1/40 players are affected by 303 and his team.