https://www.bleepingcomputer.com/news/security/bug-sent-whatsapp-into-crash-loop-caused-chat-history-loss/

Security researchers found a bug in WhatsApp that could be used to crash the messaging app in a loop on the phone of every member of a group.

The effect could be obtained by modifying a participant's phone number and sending out a message. As a result, members would no longer be able to access the group or conversation history.