On Monday evening, The Washington Post, The New York Times, BuzzFeed News, and Reuters all reported that during last week's White House meeting between President Donald Trump and Russian diplomats, Trump shared highly classified intelligence with the Russians. As president, Trump is able to declassify what he likes, but that is not, itself, why there's alarm.
In the meeting with Russian Foreign Minister Sergey Lavrov as well as Sergei Kislyak, Russia's ambassador to the United States, Trump revealed intelligence about threats to aircraft that had been shared by an ally. Under the “rules of espionage,” you don't share intelligence that was shared with you by a partner.
There is also the question of what Russia already knew and what its intelligence agencies could determine by viewing the new information in the context of their own intelligence.
Various Trump administration officials have released statements on the stories:
National Security Advisor H.R. McMaster will be issuing a further statement outside the White House shortly.
This is a developing story and will be updated as more information becomes available.