> Where does that info come from ? If it does come from the "Aircraft Control Domain, or ACD" then these two systems are probably not "completely isolated" as claimed in the article?

You are indeed right, there is a connection to the BUS that shares some information. You can also write back some of the information(flight number, flight leg etc.) back to it. However, rest of the things are read-only. So, no way to do weird things like modifying the altitude or ground speed etc.

Basically, the main computer is completely isolated from the infotainment system, except for the BUS emitting these minor information.

You can however, probably get near the main computer if you can get the jump seat ...

Disclaimer: Work in aviation tech.