US firm Tesla has updated its software after researchers from China hacked into the operating system of its electric cars.
The team from Keen Security Lab remotely manipulated the brake system on a Tesla while it was on the move, from a distance of 19km.
Using a laptop, the hackers also managed to open a car door without using a key.
Tesla has updated its software to prevent anyone else from manipulating its cars.
The hack took place after months of research and the team from Keen Security Lab posted a video of their efforts earlier this week on YouTube.
During the experiment a hacker took control of a vehicle from the passenger seat, while someone else was behind the wheel.
Using a laptop, he was able to adjust the rear-view mirror while the driver was changing lanes. The hacker also managed to open the trunk remotely, while the car was on the move.
BBC North America technology reporter Dave Lee said the experiment was notable for two reasons - the distance involved, and the sheer amount of control demonstrated.
"The good news is the security community is so far rising to the challenge of protecting cars from hackers. This hack was discovered by researchers who, as they should, went straight to Tesla before going public," he wrote.
"Tesla's cars are able to get over-the-air updates, meaning Tesla's engineers can automatically rectify the vulnerability in its cars without needing drivers needing to visit a dealership.
"And that's precisely what the company has done."