> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/websockets/websocket-handshake-manipulation.md).
# WebSocket Handshake Manipulation
WebSocket Handshake Manipulation notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Manipulating the WebSocket Handshake to Exploit Vulnerabilities
This online shop has real-time chat functionality based on **WebSockets**. / An XSS filter is present: it is aggressive but has exploitable faults.
A chat field allows you to send messages that are displayed in real time on the support agent side.
#### Initial XSS Filter Test
When sending the following payload into the chat:
```javascript
```
The server responds with the message:
* **Attack detected: Event handler**
* WebSocket connection is immediately **closed**.
After simply reloading the page, the following message appears:
* **This address is blacklisted**
The IP address is therefore temporarily blocked.
#### Contouring Blacklisting
Adding the following HTTP header when establishing the WebSocket handshake:
```http
X-Forwarded-For: 0.0.0.0
```
The server again accepts the connection. / To avoid having to add manually each time, this header is configured **permanently in the proxy**.
#### XSS Filter Contouring
Once the connection is restored, the payload is slightly modified to bypass the filter:
```javascript
```
This change of breakage and syntax allows to bypass the detection.
---
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