Apple has successfully rolled out an update (2.0.24) that helps people trace unknown AirTags.
It first released a firmware update in November that added Precision Finding, that will enable iPhone users to detect an unknown AirTag that is moving with them - say, slipped into a bag without their knowledge. This addresses one of the concerns some have with Apple's tracking device being used as a stalking tool.
Basically, if your iPhone is on, a notification will appear if an AirTag that is assigned to another user is travelling with you. A sound will also play from the AirTag itself.
It has taken a while for this update to reach all AirTags (the update is automatic and cannot be performed manually). In fact, a second update (2.0.36) has also started to rollout, but that's just a patch for a minor accelerometer issue.
The new "anti-stalking" feature requires iOS 16.2 to be installed on the victim's iPhone. It also only works with supported iPhones that have Ultra Wideband capabilities, so from iPhone 11 and up.
To find out what firmware your own AirTag is currently on, you need to go to the Find My app, tap on the AirTag in your items, then tap on the name of your AirTag in the pop-up display, it will cycle to the serial and current firmware numbers under the name.