GHSA-w836-5gpm-7r93: SiYuan has a Reflected Cross-Site Scripting (XSS) via /api/icon/getDynamicIcon

Summary

Reflected XSS in /api/icon/getDynamicIcon due to unsanitized SVG input.

Details

The endpoint generates SVG images for text icons (type=8). The content query parameter is inserted directly into the SVG <text> tag without XML escaping. Since the response Content-Type is image/svg+xml, injecting unescaped tags allows breaking the XML structure and executing JavaScript.

PoC

Payload: test</text><script>alert(window.origin)</script><text>

1. Open any note and click Change Icon -> Dynamic (Text). <img width="713" height="373" alt="image" src="https://github.com/user-attachments/assets/8a4f5ec4-81d6-46cb-8872-841cb2188ed8" />

2. Change color and paste the payload into the Custom field and click on this icon. <img width="935" height="682" alt="image" src="https://github.com/user-attachments/assets/24d28fbd-a3ce-44f1-a5bb-2cc3f711faf5" />

3. Intercept and send the request or get path from devtools <img width="1229" height="627" alt="image" src="https://github.com/user-attachments/assets/3cfb1d9a-5a23-476c-86cc-f9a7de6bbe32" /> <img width="1140" height="764" alt="image" src="https://github.com/user-attachments/assets/2657e44f-3724-4136-a53f-75068945aef0" />

4. The JavaScript payload executes afted open URL. <img width="701" height="809" alt="image" src="https://github.com/user-attachments/assets/343ad67a-e236-466b-9ec9-e4f1dea4fd5e" /> <img width="1382" height="847" alt="image" src="https://github.com/user-attachments/assets/01820d3c-c374-402a-8d72-6ea75dbd92c2" />

Impact

Arbitrary JavaScript execution in the user’s session context if the SVG is loaded directly. It also prevents using legitimate characters like < or > in icon text.

Note

Tested version: <img width="1368" height="699" alt="image" src="https://github.com/user-attachments/assets/a7466b8f-a88b-461d-8d9e-7178af7ab076" />