CVE-2026-34605 PoC — SiYuan: Reflected XSS via SVG namespace prefix bypass in SanitizeSVG ( getDynamicIcon, unauthenticated )

Title:SiYuan: Reflected XSS via SVG namespace prefix bypass in SanitizeSVG ( getDynamicIcon, unauthenticated ) (CVE-2026-34605)
Description:SiYuan is a personal knowledge management system. From version 3.6.0 to before version 3.6.2, the SanitizeSVG function introduced in version 3.6.0 to fix XSS in the unauthenticated /api/icon/getDynamicIcon endpoint can be bypassed by using namespace-prefixed element names such as <x:script xmlns:x="http://www.w3.org/2000/svg">. The Go HTML5 parser records the element's tag as "x:script" rather than "script", so the tag check passes it through. The SVG is served with Content-Type: image/svg+xml and no Content Security Policy; when a browser opens the response directly, its XML parser resolves the prefix to the SVG namespace and executes the embedded script. This issue has been patched in version 3.6.2.

SiYuan Note through version 3.6.1 is vulnerable to unauthenticated reflected Cross-Site Scripting (XSS) in the `/api/icon/getDynamicIcon` endpoint due to improper filtering of SVG elements with a namespace prefix (such as `<x:script>`). By using a namespaced script element, attackers can bypass the `SanitizeSVG` function and execute arbitrary JavaScript in the victim’s browser upon visiting a crafted link.

 id: CVE-2026-34605

info:
  name: SiYuan Note - Cross-Site Scripting
  author: ritikchaddha
  severi

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