Strange online encounter

I've talked to a random person on a known local public chat in a private message tab. Meanwhile I got a whatsapp message from a person that I know and that complete stranger online, 2 minutes later typed "You got a whatsapp message", how the hell did they know? Should I be concerned? They logged out after telling me that.



I know that it's relatively easy to get someones IP while talking to them online in such scenarios, but knowing …

chat local message privacy private public random tab whatsapp