The corresponding FAA term is "Airworthiness Directive" (AD). An AD is a very big deal.
The in-flight entertainment (IFE) systems receive navigation data from the flight deck computers so they can display the moving maps and other stuff on the entertainment displays, for those passengers who want to know "where am I", "are we there yet", "is it time to reset my watch because we've crossed a time zone and I'm trying to adjust my body clock".
I would be shocked to learn that Boeing allowed the IFE to put ANY kind of data into the flight deck computers. I'd actually expect Boeing to use a one-way interface, one that transmits but does not receive: think RS-232 with one of the pins removed. I'd be almost as shocked to learn that Airbus did something like that. However, Airbus's comment about "firewalls" does not exactly inspire me to confidence in their airplanes.
There's something else. If Mr. Roberts did in fact do what the FBI claimed he said he did, I would have expected the air up in the cockpit to have turned very blue, as the pilots said (screamed, actually) something along the lines of what the Apollo 8 crew said (screamed, actually) when their CSM did an uncommanded thruster burn. I would further expected them to take manual control immediately, get on the radio immediately, declare an emergency because of the uncommanded engine power setting change, and land at the nearest airstrip that could handle the airplane. I would further expect maintenance crews to pull the flight data recorders to find out WTF just happened.