Security Issues in Replit Agent Code

Replit apps often lack HTTPS enforcement, have no security headers, and store secrets in ways that don't transfer cleanly (leading developers to hardcode them temporarily, then forget). The development server is often used in production. Database connections may not be encrypted

Set up HTTPS with your hosting platform. Add security headers (CSP, HSTS, X-Frame-Options). Use environment variables for all secrets with your new platform's secrets management. Switch from development server to production server (gunicorn, PM2). Ensure database connections use SSL

Every Replit Agent app needs authentication — verifying who the user is — and authorization — verifying what they're allowed to do. Check that every API route and server action verifies the user's identity before processing requests. Check that users can only access their own data. A common Replit Agent pattern is adding auth to the UI but not the API, which means anyone with the endpoint URL can access data directly.

Never trust data coming from the client. Every form submission, URL parameter, and API request body should be validated server-side before processing. Use a schema validation library like Zod to define expected shapes and reject anything that doesn't match. This prevents injection attacks, data corruption, and unexpected crashes.

Configure security headers to protect against common web attacks: Content-Security-Policy to prevent XSS, Strict-Transport-Security to enforce HTTPS, X-Frame-Options to prevent clickjacking, and X-Content-Type-Options to prevent MIME sniffing. Most hosting platforms let you configure these in a headers file or configuration.

If your app handles user data, processes payments, or stores sensitive information, a professional security review is essential before launch. Our security scan ($19) checks for the most critical vulnerabilities, and our full security review service provides a comprehensive assessment with remediation guidance.