A hidden flaw in a dealer-installed car alarm could let attackers unlock vehicles and track their locations. Many owners don't know they have one.

Dealerships installed alarms in millions of vehicles—and left them in even if the buyer didn’t want them. Now researchers warn they can be hacked to unlock, track, and disable…

At least 2.2 million cars on the road today are vulnerable to an attack that allows thieves to lock and unlock doors and immobilize vehicle engines remotely via a Bluetooth…