During the Watergate scandal there was an informer pseudo named deep throat.   At that time there was a blockbuster X rated film called Deep Throat that crossed over into pop culture. The source has since been identified.
The Trump White House has a similar shadowy figure who has supplied sensitive information even prior to Melania joining Donald at the White House. Needless to say Donald has freaked out and has even accused Obama. Who is the Whit House leaker?
I believe a State Dept. source can be ruled out unless you suspect Rex.
The nature of the information suggests it is highly placed which leaves two strong possibilities. Someone embedded in the White House or the Russians via technology in the Oval Office and elsewhere.

Of course Russia has motives for this be it instigating chaos or paranoia. The tools for an operation like this has four main factors called MICE https://en.wikipedia.org/wiki/Motives_for_spying

Trump is loyalty obsessed which leaves a conundrum.
Does anyone here want to take a shot in the dark and hazard a guess who is Trump's deep throat? Miss Scarlet in the library?