From the previous discussion about Roberts' case ( https://news.ycombinator.com/item?id=9558615 and https://news.ycombinator.com/item?id=9568050 ) the general impression seemed to be that avionics are isolated from IFE and other non-critical systems so this would be impossible.

The fact that this researcher is a licensed pilot does not necessarily mean much; the pilot license only certifies that he knows how to fly a plane, not that he knows in detail about all the systems in one.