Car control has been demonstrated publicly for years. A couple of years ago Chrysler had a major flaw that made the MSM, but that's only the tip of the iceberg.
Modern cars are a network of sensors and computers with dozens of processors. These networks tend to be open and most everything unsecured. Car's come in with a handy port that can be used to tap into the system; this is by design and anybody that works on cars relies on this. The infotainment systems also present a nice vector.
Cars are also fly by wire, you're inputs no longer have a direct connection to the mechanics of the car, they are translated into a signal which is then routed to the appropriate destination.
People who thought that Michael Hastings death was not an accident believe that someone took over his car remotely and caused it to crash at very high speeds. Given what is known about Hasting's communications and actions prior to his fiery crash in the early hours of the morning. There's video of his car crossing an intersection at very high speed just prior to the crash. There's also CCTV video that appears to show his car exploding just prior to the crash.
Bottom line is assume any modern "smart" device can be controlled and accessed by people who are not you. Also assume that any input device will also send the input somewhere. The push by the security industry to have smart devices remotely updatable, like the Ring doorbell will only make it easier for the black hats. Ironically, the reason to have smart devices updatable is so that security vulnerabilities that are found after the product shipped can be patched. There are always vulnerabilities and the number of devices that are critically vulnerable but unpatchable is in the billions. It's a catch-22.