Today's what-ifs are tomorrow's WTFs.
Sounds more like the fictional liquid bomb that never could have worked outside a laboratory and has caused millions of people to waste millions of hours at airports ever since.
And in this case, millions of people are downloading millions of MP3s every day and never a "WTF". Except when they get Rickrolled.
The music system in some vehicles is tied into the same CAN-bus with everything else so that it can get signals from the same steering wheel that has the cruise controls on it and which is listened to by the TCM. There's basically no security on this bus.
You've been reading too much Neuromancer. Has this ever happened? No. If it were possible, some asshole would have done it by now.