The only other option is, as another commenter mentioned, a buffer overflow, or similar, that would allow the ACARS receiver to load a program in the FMS. In no

The only other option is, as another commenter mentioned, a buffer overflow, or similar, that would allow the ACARS receiver to load a program in the FMS. In normal operation, FMS programs are not controllable remotely. This is the clear implication in the article - compromising the ACARS receiver, then using that access to further compromise another element like the FMS. The article states that the pilot can regain control by disconnecting the AP.