The same Indian enthusiast who a year ago found out how to block WhatsApp by sending a 2,000 character, 2 KB message is back with a new exploit: now he has discovered that all you need to do is send a message with more than 4,000 emojis or more.
The science behind this exploit is pretty straightforward. The web version of WhatsApp allows you to send a maximum of 65,000 characters, but if you include a huge amount of emoji, like in this case more than 4,000, the message is sent but ends up blocking the application when its buffer overflows.
How this exploit works
Although technically it should be possible to use this exploit from the mobile application, as soon as you have included more than a thousand emojis it becomes very unstable and almost impossible to handle, making it almost impossible to send the message. It is much easier to get it from the Web version, which is the one used by Indrajeet Bhuyan, its discoverer, in this demonstration video.
The video clearly shows how easy it is to use this exploit to block anyone’s conversation, as well as blocking both the application and the web version.
I just tried it, by science, and the truth is that it is very easy block the app for mobile. In fact, on a low or mid-range phone, a much smaller number of emojis is likely to suffice. The web version, however, I was not blocked with 4,000 emoji, so presumably it also depends on the power of the PC.
What to do if you receive a message like this
If any of your contacts is so “nice” to use this technique against you and block your WhatsApp conversation, what you should do is delete the conversation without entering it.
In the app, go to the tab Chats, long press on the malicious chat and finally choose Delete chat. You can also try to delete it from the web version of WhatsApp, as it does not seem to block as easily.
A year ago, WhatsApp fixed a similar bug by limiting the maximum number of characters per message, but not the maximum number of emojis you could insert. Presumably an upcoming WhatsApp update will also introduce a emoji limit per message to a reasonable figure.
More information | Hackatrick
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