n8n Stored XSS (Form Trigger)

A Stored Cross-Site Scripting (XSS) vulnerability in n8n's Form Trigger node that can lead to session hijacking and Account Takeover (ATO).

## Vulnerability Overview
The n8n Form Trigger node allows users to create web forms for workflow automation. This vulnerability exists because user-submitted form data is stored and displayed in the n8n admin interface without proper sanitization. An attacker can submit a form with malicious JavaScript that executes when an n8n administrator views the form submissions.

## Technical Details
- **Type:** Stored XSS (CWE-79)
- **Root Cause:** Form field values submitted through the Form Trigger are rendered in the n8n execution log and data preview without HTML encoding. Malicious JavaScript in form fields executes in the context of the authenticated admin session.
- **Attack Vector:** Submit a form with XSS payload → Admin views submission → Cookie stolen

## Impact
- Session hijacking (steal admin authentication token)
- Account Takeover — attacker gains full admin access
- Access to all workflows, credentials, and connected services
- Potential RCE via workflow modification (chain with other n8n vulnerabilities)