CVE-2026-31807: SiYuan has a SVG Sanitizer Bypass via `<animate>` Element — Unauthenticated XSS

SiYuan’s SVG sanitizer (SanitizeSVG) blocks dangerous elements (<script>, <iframe>, <foreignobject>) and removes on* event handlers and javascript: in href attributes. However, it does NOT block SVG animation elements (<animate>, <set>) which can dynamically set attributes to dangerous values at runtime, bypassing the static sanitization. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint (type=8), creating a reflected XSS.

This is a bypass of the fix for CVE-2026-29183 (fixed in v3.5.9).