FBI seems to agree with me:
Internet Crime Complaint Center (IC3) | Motor Vehicles Increasingly Vulnerable to Remote Exploits

"Vulnerabilities may exist within a vehicle’s wireless communication functions, within a mobile device – such as a cellular phone or tablet connected to the vehicle via USB, Bluetooth, or Wi-Fi – or within a third-party device connected through a vehicle diagnostic port. In these cases, it may be possible for an attacker to remotely exploit these vulnerabilities and gain access to the vehicle’s controller network or to data stored on the vehicle."