The Web Security Checklist Every Startup Must Complete Before Launch

Security is the single most common area where early-stage startups cut corners—and the consequences can be company-ending. A data breach that exposes user PII doesn't just create financial liability; it destroys the trust that took months to build. At Exavel, every application we ship passes through a rigorous security checklist before a single byte of real user data touches our systems. These are the non-negotiables.

Authentication: The Front Door

Never roll your own authentication. The cryptographic complexity of securely handling passwords, session management, and token rotation is well beyond what a startup engineering team should be investing time in. Use a battle-tested solution like Auth.js (formerly NextAuth), Clerk, or Supabase Auth. Ensure you enforce Multi-Factor Authentication (MFA) for all admin accounts from day one, and implement proper rate limiting on all auth endpoints to prevent brute force attacks.

Input Validation: Trust Nothing

Every piece of data entering your system from the outside world must be treated as hostile until proven otherwise. Implement server-side validation using a schema validation library (like Zod) on every API endpoint. Never trust client-side validation alone—it's trivially bypassed. Use parameterized queries via your ORM for every database operation to eliminate SQL injection vulnerabilities entirely.

HTTPS and Security Headers

Enforce HTTPS with HTTP Strict Transport Security (HSTS) headers on every page. Beyond HTTPS, implement a comprehensive Content Security Policy (CSP) to prevent XSS attacks, X-Frame-Options to prevent clickjacking, and ensure your cookies have the HttpOnly and Secure flags set. In Next.js, these headers can be configured centrally in your next.config.ts.

Dependency Management

Modern web applications have hundreds of transitive dependencies, each representing a potential attack surface. Run npm audit as part of your CI pipeline and fail the build on high-severity vulnerabilities. Enable GitHub Dependabot for automated security patch pull requests. Regularly review your package.json and eliminate unused dependencies—every library you don't use is an attack surface you don't need.

Secrets Management

Secret credentials must never touch your code repository—not even for a single commit, because git history is permanent. Use environment variables for all secrets, ensure your .env files are in your .gitignore, and for production, use your hosting platform's secrets manager (Vercel Environment Variables, AWS Secrets Manager, etc.). Rotate all credentials immediately if you ever suspect exposure.

API Rate Limiting and DDoS Mitigation

Every publicly accessible API endpoint must have rate limiting. Without it, a trivial script can overwhelm your servers, burn through your database connections, and run up your cloud bill. Implement rate limiting at the edge using middleware, and configure your CDN or platform to absorb volumetric DDoS attacks before they reach your application layer.

Conclusion

Security isn't a feature you add later—it's a foundation you build before you open your doors. These items represent the minimum viable security posture for any production application handling user data. At Exavel, we embed this checklist into our pre-launch process for every client project, no exceptions.