The most widespread theory in House leadership is that the secret recorder and the leaker was Evan McMullin, who as a former leadership aide participated in the June 15 conversation and confirmed the private conversation to the Washington Post. (I am told that the Post, in their back-and-forth with leadership over the story, privately said that the source wasn’t McMullin. There’s no evidence that he was the leaker and I’ve reached out to him for comment.)
Evidence or not, leadership sources are privately worried that McMullin had a tape on while he sat silently through all of their confidential meetings. They’re concerned about what leaks could come next.