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.
https://goo.gl/LqCJAD
this is happening in IMO also.