The content of the message should contains the **[FUZZ]** keyword.
```json
{"auth_user":"dGVzda==", "auth_pass":"[FUZZ]"}
```
Then you can use any tools against the newly created web service, working as a proxy and tampering on the fly the content of message sent thru the websocket.
- [HACKING WEB SOCKETS: ALL WEB PENTEST TOOLS WELCOMED by Michael Fowl | Mar 5, 2019](https://www.vdalabs.com/2019/03/05/hacking-web-sockets-all-web-pentest-tools-welcomed/)
- [Hacking with WebSockets - Qualys - Mike Shema, Sergey Shekyan, Vaagn Toukharian](https://media.blackhat.com/bh-us-12/Briefings/Shekyan/BH_US_12_Shekyan_Toukharian_Hacking_Websocket_Slides.pdf)