Reporter who broke this is on Maddow now.
Two things of note.
First, sources include CURRENT Trump administration officials, concerned enough about what Trump did, leaked it.
Second, they never said Trump disclosed the source. The problem is, the substance of the intelligence, including the plot, and where it was located, would allow an intelligence service to figure that out.
Trump did this to puff out his chest some more, and show the Russians he met with that he is "in the know." As soon as it happened, various TRUMP officials exclaimed WTF is he doing? And alerted CIA, which is how it made it's way out to the press.
Tragically arrogant and reckless. The VERY THINGS he accused Clinton of, he is in spades. Buh bye, Donald. Don't let the door hit ya where the good Lord split ya.