Suppose a person has a habit of telling someone's matter to someone to whom it is supposed not to be told. e.g. I told some bad things about Mr. B to Mr. A and Mr. A character was so bad that he told my words to Mr. B; so Mr. B got angry and he told some bad things about me in turn and Mr. A told that bad things to me.
How would you describe the Mr. A's character? I think there is a word to describe this type of character; please let me know that.
Please help me.
He is a gossip, he's a leaky hose, he can't keep his mouth shut, he's a blabbermouth.
But you started it - you are the true gossip.
He can also be described as a backstabber.