Learn how to harden a Flask app using the flask-security library (a Helmet-style approach): install via pip, then add an after_request handler that sets four key headers—X-Frame-Options (SAMEORIGIN), Content-Security-Policy (restrict sources), X-XSS-Protection (1; mode=block), and X-Content-Type-Options (nosniff)—to mitigate XSS, clickjacking, and MIME-sniffing risks.