Popular messaging service WhatsApp is plagued with a major bug that allows users to message you even after you've blocked them. In addition to messaging, the loophole - which is present on both Android and iOS clients of the service - allows blocked contacts to see your status and profile details as well. The problem has a quick solution: unblock the contact and block them again. However, not many users are aware of the workaround. Obviously this is a very serious issue, so it should be fixed very soon.. but I hope WhatsApp is aware of it 😥 there are many tweets on Twitter...
Source: https://www.gsmarena.com/major_whatsapp_bug_allows_messages_from_blocked_contacts-news-31259.php