Summary

A cross site scripting vulnerability has been found in the web application chat frontend when using echarts. User or llm inputs containing echarts containing a specific javascript payload will be executed.

Details

The problematic code is in web/app/components/base/markdown-blocks/code-block.tsx:208 and web/app/components/base/markdown-blocks/code-block.tsx:253:

        try {
          // eslint-disable-next-line no-new-func, sonarjs/code-eval
          const result = new Function(`return ${trimmedContent}`)()

The code inside new Function () is executed as immediately-invoked function expression (IIFE).

PoC

• Run a chat app
• Input the payload

```echarts
  ({
    title: { text: 'Test XSS' },
    series: [],
    _x: (() => {
      alert('Hello');
      return 1;
    })()
  })

• Javascript is executed

Impact

Full arbitrary JavaScript execution in the victim’s browser, in the context of the app. That means:

• Account/session takeover via log
• Data exfiltration from the UI (chat history, files, secrets visible in DOM).
• Unauthorized actions via in‑app APIs using the victim’s session.
• If the payload is saved (chat history), it becomes stored XSS and hits any viewer later. If not saved, it’s reflected DOM XSS for the current viewer.