Lab 280 — InkWell — CSP Bypass via JPEG Polyglot XSS

hackadvisor

Task: InkWell accepts JPEG avatars and raw comments under a self-only CSP, then sends an admin bot to reported comments. Solution: A same-origin JPEG/JavaScript polyglot loaded by a stored script tag executed in HeadlessChrome and leaked the flag cookie through an Interaction Server path.