https://www.bleepingcomputer.com/news/security/googles-indexing-of-whatsapp-numbers-raises-privacy-concerns/

Google is indexing the phone numbers used on WhatsApp, and a researcher is concerned that it could cause privacy issues or be used for malicious purposes.

Earlier this year, Bleeping Computer reported how invite links to private groups of messaging apps like WhatsApp and Telegram were visible on Google, letting anyone join the groups.