'Days of Our Lives' Star Jessica Serfaty Alerted to Tracker in Her Car

Soap opera/social media star Jessica Serfaty's learning just how invasive tech can be ... after finding out someone's been tracking her every move with a secretly-placed Apple AirTag.

Law enforcement sources tell TMZ, Jessica -- who plays Sloan-Petersen Brady on "Days Of Our Lives" -- was hanging out in Malibu when her phone pinged her about the AirTag in her Range Rover.

We're told Jessica was immediately concerned, because she hadn't put any such device in her SUV, nor had she seen one. She worried someone had stashed it in her car -- perhaps in the engine compartment -- to keep tabs on her.

Sheriff's deputies showed up and searched the vehicle, but couldn’t find the AirTag. It's unclear if it fell off, or someone removed it.

Cops took a report for unauthorized use of an electronic device ... and our sources say detectives are now on the hunt, trying to track down the AirTag user's info by using Jessica's phone.

We're told operating theories on the suspect's motive include stalking, burglary or car theft -- none of which can make Jessica feel too comfortable.