A group of researchers has discovered a bug in WhatsApp that could allow hackers to crash it and delete group chats forever.

The exploit was discovered by Check Point and builds on previous research they have done regarding WhatsApp’s security. The researchers’ report goes into quite a bit of technical detail regarding the bug, but here are the basic steps:

• A hacker would need to gain access to a particular WhatsApp group chat in order to be able to compromise it.
• Using standard development and penetration-testing tools, the hacker would then gain access to the key-pair used to encrypt the messages for that particular group.
• The hacker can then intercept and edit various parameters of messages, such as the originating phone number, replacing numbers with non-digit characters.

Once the message is sent with the modified information, WhatsApp will crash, and continue crashing even after it is reopened. It can only be stopped by deleting and reinstalling it. Unfortunately, even if everyone deletes and reinstall their app, all the data in the group chat thread is permanently lost.

Obviously, given the nature of gaining access to a specific group and the skills required to access the encryption keys for that particular group, this is not a bug that is a widespread threat. In addition, Check Point reported the bug to WhatsApp developers after finding it in August and only reported it publicly today, after the bug has been fixed.

Even so, for users who have not updated to version 2.19.246 or later, the potential for targeted attacks is very high. Researchers Dikla Barda, Roman Zaikin and Yaara Shriki voiced concern about the implications in their report:

“In WhatsApp there are many important groups with valuable content. If an attacker uses this technique and crashes one of these groups all chat history will be gone and further communication would be impossible.

“The impact of this vulnerability is potentially tremendous, since WhatsApp is the main communication service for many people. Thus, the bug compromises the availability of the app which is a crucial for our daily activities.”