Hackers are smart. Could they hack a self-driving car through its CD drive? From what I understand, malicious code could be uploaded to the driverless car via CD which could give them access to brakes, windscreen wipers, sensors, etc. (all of which could be used to potentially commit murder or hold the car ransom).
Not on a well-designed car

The CD player is part of the media system. It's likely that the media system has a number of security vulnerabilities, and a malicious CD can probably take control of the media system. It would be difficult to fix this without either greatly increasing the cost, or restricting the functionality of this.

The car control systems - the CAN bus - should be strongly separated from the media systems. In previous attacks, like Jeep hacking, attackers have been able to break across from the media system to the CAN bus. However, this represents poor design and implementation. The two systems should be kept separate - or at least, have a highly restricted interface - and it is possible to do that at reasonable cost.

Whether any future driverless cars will be well designed remains to be seen.
