This is pretty fun. I wonder if they still hide them in plain sight.
From the reuters piece:
Another CIA officer in the meeting then showed Hosseini a covert communications system he could use to reach his handlers: a rudimentary Persian-language soccer news website called Iraniangoals.com. Entering a password into the search bar caused a secret messaging window to pop up, allowing Hosseini to send information and receive instructions from the CIA.
I'd love to find a list of these kind of secret doors. They are just so silly and neat.