Building secure applications: best practices

Security breaches cost companies millions in damages and lost trust. Yet most startups treat security as an afterthought.

Here are the essential security practices you must implement from day one.

Authentication Security

Never Roll Your Own:

Use proven authentication services:

• Supabase Auth
• Clerk
• Auth0
• NextAuth.js

These services handle:

• Password hashing and salting
• Session management
• Multi-factor authentication
• OAuth integrations
• Security best practices

Password Requirements:

• Minimum 12 characters
• Check against common password lists
• Enforce MFA for admin accounts
• Implement account lockout after failed attempts

Data Protection

Encryption:

• In transit: Always use HTTPS (TLS 1.3)
• At rest: Encrypt sensitive data in database
• Environment variables: Never commit secrets to git

Database Security:

• Use Row Level Security (RLS) in Supabase
• Parameterized queries to prevent SQL injection
• Principle of least privilege for database users
• Regular backups with encryption

API Security

Rate Limiting:

Implement rate limiting on all endpoints:

• Per IP address
• Per authenticated user
• Per API endpoint

Use Upstash Rate Limiting or Vercel's built-in protection.

Input Validation:

• Validate all user inputs
• Sanitize HTML to prevent XSS
• Use schema validation (Zod)
• Reject unexpected data types

API Keys:

• Rotate regularly
• Store in environment variables
• Use different keys for dev/prod
• Monitor usage for anomalies

Frontend Security

XSS Prevention:

• React automatically escapes content
• Be careful with dangerouslySetInnerHTML
• Sanitize user-generated HTML
• Use Content Security Policy headers

CSRF Protection:

• Use SameSite cookies
• Implement CSRF tokens
• Verify origin headers

Infrastructure Security

Vercel Configuration:

• Enable automatic HTTPS
• Set security headers
• Enable DDoS protection
• Use environment variables for secrets

Monitoring:

• Log all authentication attempts
• Monitor for unusual patterns
• Set up alerts for suspicious activity
• Regular security audits

Compliance

GDPR Requirements:

• User consent for data collection
• Right to data export
• Right to be forgotten
• Privacy policy
• Cookie consent

SOC 2 Considerations:

• Access controls
• Audit logs
• Incident response plan
• Employee training

Security Checklist

Before launch, ensure:

1. HTTPS everywhere
2. Authentication service configured
3. Rate limiting implemented
4. Input validation on all forms
5. SQL injection prevention
6. XSS protection
7. CSRF tokens
8. Secure session management
9. Environment variables secured
10. Regular backups configured
11. Monitoring and logging active
12. Security headers set

Ongoing Security

Security isn't one-time:

• Regular dependency updates
• Security patches within 24 hours
• Quarterly security reviews
• Annual penetration testing
• Team security training

Building secure applications isn't optional. Make security a priority from day one to protect your users and your business.