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David Friedman
David Friedman

Posted on • Originally published at appbrewers.com

Web App Security Checklist 2026: Protect Your Startup from Day One

Security is not a feature you add later. It is a foundation you build from day one. Here is our production checklist.

By David Friedman, Founder of AppBrewers


We have audited 20+ web apps for security. The same vulnerabilities appear repeatedly. Here is the checklist we use for every project.


Authentication

  • [ ] Use OAuth 2.0 / OpenID Connect (Firebase Auth, Clerk, Auth0)
  • [ ] Enforce strong passwords (8+ chars, complexity requirements)
  • [ ] Implement brute-force protection (rate limiting)
  • [ ] Use secure session tokens (HTTPOnly, SameSite, Secure flags)
  • [ ] Add multi-factor authentication for admin roles

Authorization

  • [ ] Verify permissions on every API endpoint (server-side)
  • [ ] Use Role-Based Access Control (RBAC) or Attribute-Based Access Control (ABAC)
  • [ ] Never trust client-side permission checks
  • [ ] Validate resource ownership (user A cannot access user B's data)

Data Protection

  • [ ] Encrypt data at rest (AES-256)
  • [ ] Encrypt data in transit (TLS 1.3 minimum)
  • [ ] Hash passwords with bcrypt / Argon2 (never MD5 or SHA1)
  • [ ] Mask sensitive data in logs
  • [ ] Implement GDPR-compliant data deletion

Input Validation

  • [ ] Validate all inputs server-side (never trust client)
  • [ ] Sanitize HTML to prevent XSS
  • [ ] Use parameterized queries (prevent SQL injection)
  • [ ] Validate file uploads (type, size, content scan)
  • [ ] Set strict Content Security Policy headers

Infrastructure

  • [ ] Use HTTPS everywhere (HSTS enabled)
  • [ ] Keep dependencies updated (automated scanning)
  • [ ] Implement DDoS protection (Cloudflare, AWS Shield)
  • [ ] Enable Web Application Firewall (WAF)
  • [ ] Regular security audits and penetration testing

Monitoring

  • [ ] Log all authentication attempts
  • [ ] Alert on suspicious activity (impossible travel, brute force)
  • [ ] Monitor for dependency vulnerabilities (Snyk, Dependabot)
  • [ ] Incident response plan documented

Common Vulnerabilities We Fix

Vulnerability Impact Fix
XSS Session hijacking CSP + input sanitization
CSRF Unauthorized actions SameSite cookies + tokens
SQL Injection Database access Parameterized queries
IDOR Data leakage Server-side authorization
Insecure Direct Object Reference Account takeover UUIDs + permission checks

Need a Security Audit?

We build secure web apps from the ground up. Auth, encryption, compliance. Penetration testing available. Malta-based security team.


Originally published on the AppBrewers Blog.

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