WhatsApp security bug lets anyone join group chats without admin permission, Facebook denies
"The confidentiality of the group is broken as soon as the uninvited member can obtain all the new messages and read them."
11 Jan 2018 ... "The confidentiality of the group is broken as soon as the uninvited member ... lets anyone join group chats without admin permission, Facebook denies ... ways of confirming who will receive a message prior to it being sent.