CVE-2026-86062: lightrag-hku: Stored Cross-Site Scripting (XSS) in the LightRAG WebUI chat/answer renderer via ingested content

The LightRAG WebUI renders assistant/answer chat content as raw HTML — react-markdown is configured with rehypePlugins={[rehypeRaw]} and skipHtml={false} and no HTML sanitizer (rehype-sanitize), element allow-list, or custom urlTransform. Because answer content is derived from user-ingested documents, an attacker who can add a single document can store an HTML/JavaScript payload that executes in the browser of any user who later retrieves it (typically an administrator), leading to auth-token theft from localStorage and full API takeover. No authentication is required in the default configuration.