CVE-2026-29183

### Summary An unauthenticated reflected XSS vulnerability exists in the dynamic icon API endpoint: - `GET /api/icon/getDynamicIcon` When `type=8`, attacker-controlled `content` is embedded into SVG output without escaping. Because the endpoint is unauthenticated and returns `image/svg+xml`, a crafted URL can inject executable SVG/HTML event handlers (for example `onerror`) and run JavaScript in the SiYuan web origin. This can be chained to perform authenticated API actions and exfiltrate sensitive data when a logged-in user opens the malicious link. ### Details The issue is caused by unsafe output construction and incomplete sanitization: 1. **Endpoint is exposed without auth middleware** - Source: https://github.com/siyuan-note/siyuan/blob/master/kernel/api/router.go#L27-L37 - `GET /api/icon/getDynamicIcon` is registered in the unauthenticated section. 2. **User input is inserted into SVG via string formatting** - Source: https://github.com/siyuan-note/siyuan/blob/master/kernel/api/icon.go#L115-L175 - Source: https://github.com/siyuan-note/siyuan/blob/master/kernel/api/icon.go#L537-L585 - In `generateTypeEightSVG`, `%s` directly injects `content` into `<text>...</text>` without XML/HTML escaping. 3. **Sanitizer only removes `<script>` tags** - Source: https://github.com/siyuan-note/siyuan/blob/master/kernel/util/misc.go#L235-L281 - `RemoveScriptsInSVG` removes `<script>` nodes, but does not remove dangerous attributes (`onerror`, `onload`, etc.) or unsafe elements. As a result, payloads such as `</text><image ... onerror=...><text>` survive and execute. ### PoC #### Minimal browser execution PoC Open this URL in a browser: ```http GET /api/icon/getDynamicIcon?type=8&content=%3C%2Ftext%3E%3Cimage%20href%3Dx%20onerror%3Dalert(document.domain)%3E%3C%2Fimage%3E%3Ctext%3E ``` Example full URL: ```text http://127.0.0.1:6806/api/icon/getDynamicIcon?type=8&content=%3C%2Ftext%3E%3Cimage%20href%3Dx%20onerror%3Dalert(document.domain)%3E%3C%2Fimage%3E%3Ctext%3E ``` Expected result: - JavaScript executes (`alert(document.domain)`), confirming reflected XSS. #### Authenticated impact demonstration If a victim is authenticated in the same browser session, JavaScript running in origin can call privileged APIs and exfiltrate returned data. ### Impact This is a reflected XSS in an unauthenticated endpoint, with realistic account/data compromise impact: - Arbitrary JavaScript execution in SiYuan web origin. - Authenticated action abuse via same-origin API calls. - Sensitive data exposure (notes/config/API responses) from victim context. - Potential chained server-impact actions depending on victim privileges and deployment mode.

SiYuan: Unauthenticated Reflected XSS via SVG Injection in /api/icon/getDynamicIcon Endpoint in github.com/siyuan-note/siyuan/kernel