A serious security flaw in Watab allows anyone to spy on your conversations. How so?

They found that if anyone can control servers, it will allow them to add people to their private chat groups. This person may be the employees themselves, or the pirates, or the governments that request free access to this information legally.

Once someone penetrates the conversation, they will be able to access confidential information for everyone within the group.

This means that he will be able to see all future messages, but he won't be able to see the previous messages.