HeyForm Vulnerable to Stored XSS via Unauthenticated SVG File Upload

HeyForm is an open-source form builder. Prior to version 3.0.0-rc.7, the /api/upload endpoint allows unauthenticated file uploads including SVG files. Uploaded SVGs are stored in the static assets directory and served with Content-Type: image/svg+xml by Express's serve-static middleware, allowing an attacker to achieve stored cross-site scripting (XSS) on the heyform domain without any authentication. Version 3.0.0-rc.7 contains a patch for the issue.