Jordan Wildon, a journalist from the German publication DW News, has discovered that Google was indexing approximately 470,000 WhatsApp group invites. These invites would allow anyone to enter a private chat group. WhatsApp has already fixed the flaw by removing the listings from Google as well as by adjusting the code related to chat invitation links. While most of the chats didn't have sensitive information, it was discovered that one of them was for NGOs accredited by the United Nations. Motherboard was able to enter the chat group and see all the 48 participants as well as their phone numbers.
According to WhatsApp, the links that showed up on Google search were those that were shared in searchable public channels. The Facebook-owned app wants to remind its users that they shouldn't share invitation links on publicly searchable sites. If you're going to keep your chat group private, make sure the participants won't share these invites in public spaces.