It's a way too common practice by kids to create WhatsApp groups with EVERYONE in their contacts as members.
Then you're just added to a group with complete randos who can immediately see your phone number and they can start posting whatever.
I've had cases where my kid has been added to a group along with older kids and their posts have not been exactly SFW. I've got zero recourse in those cases, I don't know who any in the group are. I taught my kid to remove themselves from any suspicious groups immediately and that has curbed it for now.
Then you're just added to a group with complete randos who can immediately see your phone number and they can start posting whatever.
I've had cases where my kid has been added to a group along with older kids and their posts have not been exactly SFW. I've got zero recourse in those cases, I don't know who any in the group are. I taught my kid to remove themselves from any suspicious groups immediately and that has curbed it for now.