A flaw was found in the messaging app WhatsApp just recently where search engines could dish out private information on its users. While the "flaw" is claimed to be fixed, it does not really go down well with users that WhatsApp had forgotten to prevent bots from search engines in indexing the Click to Chat links in WhatsApp.
The fix of the problem was reported by TechCrunch who reports that the flaw was initially found by the security researcher Athul Jayaram who claims as many as 300.000 phone numbers may have been indexed by Google, and others have found the error before, back in February. Facebook says that the phone numbers found by Jayaram were old cached searches and not new ones and that they will be removed when re-indexing, and that they were already working on a solution before Jayaram went public with the bug.