I can't remember exactly which book, but the book pointed out how easy it could be.
Ignore messing around with firmware etc. The book foretold the story that someone would be using a online take out service/delivery service and they had setup all their allergies so that any restaurant saw a red flag and to be careful what goes in the meal. Someone hacks into just-eat or whomever the provider is. The customers Peanut allergy suddenly goes away on the notes and the dish is prepared as normal a week later. Instant severe incident if not death.
I'm so glad I don't have food allergies.