Let us not forget the UN was chuck full of commies. The Norks had the mission plans before the pilots. The pilots would be greeted by name over their radios before they got wheels up.
That little known fact is exactly correct. After MacArthur's success at Inchon the commies in the US and the UN made spying on the US Armed Forces a top priority. Only when things were happening so quickly on the battlefield that DC was left out of the loop did US Armed Forces start to have real success.