Web Security Best Practices for Modern Applications

Web security is not optional. Every web application is a target. Security must be integrated into development practices, not bolted on after launch. The cost of prevention is a fraction of the cost of a breach.

Cross-Site Scripting (XSS) prevention: sanitize all user input, use Content Security Policy headers, escape output in HTML contexts, and use frameworks (React, Vue) that auto-escape by default. Never use dangerouslySetInnerHTML with user content.

Cross-Site Request Forgery (CSRF) protection: use anti-CSRF tokens for state-changing requests, implement SameSite cookie attributes, and verify the Origin header. Modern frameworks include CSRF protection, but verify it is enabled.

Authentication security: hash passwords with bcrypt or Argon2 (never store plain text), implement rate limiting on login endpoints, require strong passwords, and offer multi-factor authentication (MFA).

JWT security: use short expiration times (15-60 minutes), implement refresh token rotation, store tokens in httpOnly cookies (not localStorage), and validate tokens on every request. Never store sensitive data in JWT payloads.

SQL injection prevention: use parameterized queries or ORM libraries (never concatenate user input into SQL). Validate input types and lengths. Apply the principle of least privilege to database connections.

HTTPS everywhere: enforce HTTPS with HSTS headers (Strict-Transport-Security). Use TLS 1.3. Redirect all HTTP requests to HTTPS. Ensure all resources (images, scripts, APIs) load over HTTPS.

Security headers: Content-Security-Policy (restricts resource loading), X-Frame-Options (prevents clickjacking), X-Content-Type-Options (prevents MIME sniffing), and Referrer-Policy (controls referrer information).

Dependency security: run npm audit regularly, use Dependabot or Snyk for automated vulnerability scanning, and update dependencies promptly when security patches are released. Third-party packages are a common attack vector.

Security monitoring: implement logging for authentication events, failed access attempts, and suspicious patterns. Set up alerts for anomalies. Have an incident response plan before you need one.