n8n Stored XSS (LangChain Chat Trigger)

A Stored XSS vulnerability in n8n's LangChain Chat Trigger node that leads to user data disclosure.

## Vulnerability Overview
The LangChain Chat Trigger in n8n allows building AI-powered chatbot workflows. This vulnerability exists because chat messages are rendered without proper sanitization in the n8n execution interface. An attacker can inject malicious JavaScript through the chat interface that executes when administrators view the conversation history.

## Technical Details
- **Type:** Stored XSS (CWE-79)
- **Root Cause:** Chat messages from the LangChain Chat Trigger are stored with HTML content and rendered without escaping in the n8n execution log viewer. The chat widget allows rich text input that is not sanitized.
- **Trigger:** An attacker sends a chat message containing JavaScript to the LangChain Chat Trigger endpoint.

## Impact
- Disclosure of user data from the n8n execution context
- Access to workflow execution data and credentials
- Session token theft for account takeover