Debug mode enabled in production exposes security vulnerabilities

Running Flask with FLASK_ENV=development or debug mode enabled in production environment displays detailed error traces and enables interactive debugger, exposing internal application details to attackers.

Set FLASK_ENV to 'production' (or omit it) before deploying. Ensure debug mode is off. Never run 'flask run' directly in production; use production WSGI servers like Gunicorn or uWSGI instead.