Researchers successfully use AirTag network to send messages - iOS Discussions on AppleInsider Forums
Security researchers investigating the Find My network used by Apples AirTags, have been able to piggyback on the system to send data that Apple can neither monitor nor, apparently, prevent. Apples Find My network could be used to relay short messages Its not something that can be easily replicated, nor is it something that could mean AirTags users face any issues of malware. However, it is reportedly possible for the Find My network to be subverted to send encoded messages ...
Source: appleinsider.com