Langflow – Stored XSS via Malicious SVG Upload

The ‘/api/v1/files/images/{flow_id}/{file_name}’ endpoint serves SVG files with the ‘image/svg+xml’ content type without sanitizing their content.

Since SVG files can contain embedded JavaScript, an attacker can upload a malicious SVG that executes arbitrary JavaScript when viewed by other users, leading to stored cross-site scripting (XSS). This allows stealing authentication tokens stored in cookies, including JWT access and refresh tokens.