A German security researcher who goes by the alias "stacksmashing" posted a YouTube video detailing how he was able to dump the firmware of an Apple AirTag. Furthermore, he was able to inject a custom firmware that changed the AirTag's "Lost Mode" function. This could open the door to more malicious jailbreaks of AirTags in the future.
https://www.notebookcheck.net/Security-researcher-successfully-hacks-and-jailbreaks-an-Apple-AirTag.539222.0.html
I was unaware that removable batteries that can be swallowed by children was a privacy concern. Learn something new every day...