Hello, I'm playing a modpack called FTB Revelation and in the chat a player said something while I was solo here is the message: (User#656E0 :where are you haha)
is this a mod? Because I directly left the world for fear of hack
That would be the MineTogether mod, which you can safely remove. Don't worry, your world has not been hacked, it's an intended mechanic of the mod to allow chatting with others even while in single player.
