Invite links for WhatsApp and Telegram groups that may not be intended for public access are available through simple lookups on popular web search engines. Both companies took some steps to protect the privacy of their users but more effort is necessary to make the links completely non-discoverable via public searches. The issue was signaled on Friday by Jordan Wildon, multimedia journalist at Deutsche Welle, who warned that the lapse allowed the discovery of some unexpected, even groups for illegal activities. WhatsApp made a first step towards keeping private the invite links by removing the listings from Google.
Source: https://www.bleepingcomputer.com/news/security/whatsapp-telegram-group-invite-links-leaked-in-public-searches/