Security isn’t something you bolt on at the end of a project. It needs to be baked into every layer of your application from day one. After years of building web applications and conducting security reviews, we’ve distilled our approach into a practical checklist.
Authentication & Authorization
The most common vulnerabilities we see in client codebases start with authentication. Here’s what to get right:
- Never store passwords in plain text. Use bcrypt or Argon2 with a cost factor of at least 12.
- Implement rate limiting on login endpoints. Brute force attacks are trivially easy without it.
- Use HTTP-only, secure cookies for session tokens. Never store JWTs in localStorage — it’s an XSS attack waiting to happen.
- Validate permissions on every API endpoint. Frontend checks are UX, backend checks are security.
Input Validation & Injection
SQL injection still makes the OWASP Top 10 because developers still concatenate user input into queries.
- Use parameterized queries everywhere. No exceptions.
- Validate and sanitize all user input on the server side. Client-side validation is for UX only.
- Implement Content Security Policy (CSP) headers to mitigate XSS attacks.
- Escape output in templates. Most modern frameworks do this by default, but verify.
Infrastructure
- Use HTTPS everywhere. There’s no excuse in 2026 with free Let’s Encrypt certificates.
- Keep dependencies updated. Run
npm auditor equivalent regularly. - Don’t expose stack traces or debug info in production. Configure error handling properly.
- Set security headers: HSTS, X-Content-Type-Options, X-Frame-Options, Referrer-Policy.
The Bottom Line
Security is a spectrum, not a checkbox. Start with these fundamentals and build from there. The cost of fixing a vulnerability in production is orders of magnitude higher than preventing it during development.