Egyptian security researcher Mohamed A. Baset has discovered a severe information disclosure vulnerability in Facebook. The vulnerability could have allowed anyone to expose Facebook page administrator profiles, which is otherwise not supposed to be public information. Facebook has now patched this information disclosure issue, but people who have already received one such page invitation can still find out admin details from the invitation emails. Baset claimed to have discovered the vulnerability in less than 3 minutes without any kind of testing or proof of concepts, or any other type of time-consuming processes.
Source: https://thehackernews.com/2018/02/find-facebook-page-admin.html