Korean automakers Hyundai and Kia have been forced to release software updates for some of their models after a viral TikTok challenge taught users how to hack their cars. So far, however, the update is only available for about one million cars out of the four million total that need the security patch.

It all started with the “Kia Challenge”, which appeared back in May on the TikTok platform. It demonstrated how the “Kia Boys” use USB cables to start cars. Soon, car owners faced massive thefts and began suing automakers for lack of response. The class-action lawsuit alleges that some Hyundai and Kia models lack engine immobilizers, a common anti-theft device. This makes it easier for attackers to gain access.

Owners of models such as the 2017-2020 Hyundai Elantra, 2015-2019 Hyundai Sonata, 2020-2021 Hyundai Venue can visit their local dealerships to install the anti-theft system upgrade, Hyundai said in a press release. The update includes an electromagnetic anti-theft sticker, a longer alarm and a requirement to have a physical key to start the car. Updates for other models will be available by June this year.

Meanwhile, Hyundai and Kia have provided about 26,000 theft-deterrent steering wheel locks to car owners, according to the US National Highway Traffic Safety Administration. The government agency had to intervene after Kia Challenge thefts led to at least 14 reported crashes and eight fatalities, turning it into a public safety issue.