one good possibility is Ivanka to Jared then to the opposition. Jared looks like he would do in anybody (including DJT) to try to gain a better position. I think he's the mole. That would mean he delivers the info to his handlers and they release to the press. Harder trail to follow.

If it's Conway, she would leak directly to the press.

If it's his wife, she's leaking to the Secret Service surrounding her and one of them is the leak.

I think those are the 3 choices.

Unless NSA has them all bugged and those people are behind it. That would mean military trials for them if they're caught at it....so, I am a little hesitant to think that would be risked by any perps over there.