Hyundai and Kia are offering free software updates for millions of their cars in response to a rash of car thefts inspired by a viral social media challenge on TikTok.

The so-called “Kia Challenge” on the social media platform has led to hundreds of car thefts nationwide, including at least 14 reported crashes and eight fatalities, according to the National Highway Traffic Safety Administration. Thieves known as “the Kia Boyz” would post instructional videos about how to bypass the vehicles’ security system using tools as simple as a USB cable.

The thefts are reportedly easy to pull off because many 2015-2019 Hyundai and Kia vehicles lack electronic immobilizers that prevent thieves from simply breaking in and bypassing the ignition. The feature is standard equipment on nearly all vehicles from the same period made by other manufacturers.

Hyundai and its subsidiary Kia are offering to update the “theft alarm software logic” to extend the length of the alarm sound from 30 seconds to one minute. The vehicles will also be updated to require a key in the ignition switch to turn the vehicle on.

The software upgrade modifies certain vehicle control modules on Hyundai vehicles equipped with standard “turn-key-to-start” ignition systems. As a result, locking the doors with the key fob will set the factory alarm and activate an “ignition kill” feature so the vehicles cannot be started when subjected to the popularized theft mode. Customers must use the key fob to unlock their vehicles to deactivate the “ignition kill” feature.

Here’s what the software update will do, according to Hyundai:

The software upgrade modifies certain vehicle control modules on Hyundai vehicles equipped with standard “turn-key-to-start” ignition systems. As a result, locking the doors with the key fob will set the factory alarm and activate an “ignition kill” feature so the vehicles cannot be started when subjected to the popularized theft mode. Customers must use the key fob to unlock their vehicles to deactivate the “ignition kill” feature.

There hasn’t been a nationwide accounting of how many Hyundai and Kia vehicles have been stolen, but stats from individual cities provide some sense of how viral the trend has become. In Milwaukee, for example, police report that 469 Kias and 426 Hyundais were stolen in 2020. Those numbers spiked the following year to 3,557 Kias and 3,406 Hyundais, according to NPR.

Approximately 3.8 million Hyundais and 4.5 million Kias are eligible for the software update free of charge, for a total of 8.3 million cars. Vehicle owners are instructed to take their cars to a local dealership, where technicians will install the upgrades in less than an hour. The upgraded vehicles will also get a window decal indicating they’ve been equipped with anti-theft technology.

Starting this week, owners of 2017-2020 Elantra, 2015-2019 Sonata, and 2020-2021 Venue vehicles are eligible for the update. Additional models, including Kona, Palisade, and Santa Fe vehicles, will be serviced starting June 2023. Customers can input their vehicle’s VIN number at this website to find out when they’re eligible for the upgrade. Kia will roll out its phased approach later this month.

Previously, Hyundai was charging owners at least $170 for security kits to fix the issue. With installation and labor, those costs could soar to $500. Hyundai and Kia were also offering some owners wheel locks to prevent thefts. NTSA says the companies have handed out 26,000 wheel locks since November 2022.