Reverse Engineering WhatsApp Encryption for Chat Manipulation and More

As of early 2018, the Facebook-owned messaging application, WhatsApp, has over 1.5 billion users with over one billion groups and 65 billion messages sent every day. WhatsApp end-to-end encryption ensures only you and the person you're communicating with can read what's sent, and nobody in between, not even WhatsApp. However, we managed to reverse engineer WhatsApp web source code and successfully decrypted WhatsApp traffic. During the process we translated all WhatsApp web functions to python and created Burpsuit extension that you can use to investigate WhatsApp traffic and extend in order to find vulnerabilities.

During the process we unveiled new vulnerabilities that could allow threat actors to intercept and manipulate messages sent in both private and group conversations, giving attackers immense power to create and spread misinformation from what appear to be trusted sources.

Our team observed three possible methods of attack exploiting this vulnerability – all of which involve social engineering tactics to fool end-users. A threat actor can:

• Send a private message to another group participant that is disguised as a public message for all, so when the targeted individual responds, it's visible to everyone in the conversation.
• Use the 'quote' feature in a group conversation to change the identity of the sender, even if that person is not a member of the group.
• Alter the text of someone else's reply, essentially putting words in their mouth.