Two popular car alarm systems have fixed security vulnerabilities that allowed researchers to remotely track, hijack and take control of vehicles with the alarms installed. The systems, built by Russian alarm maker Pandora and California-based Viper (or Clifford in the U.K.), were vulnerable to an easily manipulated server-side API, according to researchers at Pen Test Partners, a U.K. cybersecurity company. In their findings the API could be abused to take control of an alarm systems user account and their vehicle.

Its because the vulnerable alarm systems could be tricked into resetting an account password because the API was failing to check if it was an authorized request, allowing the researchers to log in. Although the researchers bought alarms to test, they saidanyone could create a user account to access any genuine account or extract all the companies user data. The researchers said some three million cars globally were vulnerable to the flaws (since fixed).

In one example demonstrating the hack, the researchers geolocated a target vehicle, tracked it in real time, followed it, remotely killed the engine and forced the car to stop, then unlocked the doors. The researchers said it wastrivially easy to hijack a vulnerable vehicle. Worse, it was possible to identify some car models, making targeted hijacks or high-end vehicles even easier.

According to their findings, the researchers also found they could listen in on the in-car microphone, built-in as part of the Pandora alarm system for making calls to the emergency services or roadside assistance. Ken Munro, founder of Pen Test Partners, told TechCrunch this was theirbiggest project.

The researchers contacted both Pandora and Viper with a seven-day disclosure period, given the severity of the vulnerabilities. Both companies responded quickly to fix the flaws.

When reached, Vipers Chris Pearson confirmed the vulnerability has been fixed.If used for malicious purposes, [the flaw] could allow customers accounts to be accessed without authorization. Viper blamed a recent system update by a service provider for the bug and said the issue wasquickly rectified.