From the December 1 edition of Fox News' Shepard Smith Reporting:
JOHN ROBERTS: I learned from a source with intimate and full knowledge of the investigation, and this is a single source but is a very, very knowledgeable source, that the Trump transition official who was not named in the court documents, only called a “PTT official,” the one with whom Michael Flynn spoke on December 29 about what to say to Sergei Kislyak, the Russian ambassador to the United States, is K.T. McFarland, who was his deputy national -- about to become the deputy national security adviser, was certainly his deputy during the transition and is now the U.S. ambassador to Singapore. Running some more traps on this, but again, a source with full knowledge of the investigation and a person who has seen all of the information that Flynn provided to investigators says that that unnamed official in the DOJ charging document is K.T. McFarland.
SHEPARD SMITH: K.T. McFarland was to work for the administration, and did for a short time. She's a former Fox News contributor that viewers may recognize here.