Nearly 5 million Kia and Hyundai vehicles that are vulnerable to theft have not been looked at despite owners being notified of free repairs to remedy the issue, Fox 26 reports.

In an effort to encourage more drivers to address the issue, CARFAX has teamed up with the auto manufacturers to spread awareness, providing data that shows 4.9 million vehicles in the United States have failed to receive repairs.

Thefts of certain Kia and Hyundai vehicles escalated following the popularity of a video on TikTok demonstrating how to bypass security. Vehicles at risk include 2010 to 2021 model years that use a key as opposed to a key fob.

According to Patrick Olsen with CARFAX, these vehicles are vulnerable due to the lack of an immobilizer. As immobilizers are not federally required, there aren’t grounds to issue a recall over the issue. Kia and Hyundai have implemented immobilizers in their vehicles since 2021, rendering newer models safe.

Though owners of affected vehicles have been mailed letters from Kia and Hyundai informing them of the problem, nearly five million still have gone unchecked. Olsen said that the fixes will typically be either a software upgrade or a steering wheel block.