G.I. joe or G.I.jane
a person who can't keep their mouth shut and will tell everyone your secrets even if they're still in the room.
My coworker is a G. I. Joe. He told my boss I was late just because he was mad I didn't text him first.
My neighbor is a G. I. Jane. She told my dog I was a bad pet to my mom.
My brother is a G. I. Joe. He told my crush I was a weirdo just to make him laugh.