Complete Website Security Checklist for 2025

Introduction

Website security is an ongoing process, not a one-time setup. Cyber threats evolve constantly, and staying protected requires regular attention to your security posture. This comprehensive checklist covers all the essential security measures every website should implement in 2025.

SSL/TLS Configuration

SSL/TLS is the foundation of web security. Proper configuration ensures encrypted communication between your users and your server.

Essential SSL/TLS Checks

• [ ] HTTPS Enforced: All pages redirect to HTTPS
• [ ] Valid Certificate: SSL certificate from a trusted Certificate Authority
• [ ] Proper Redirects: HTTP to HTTPS redirect (avoid redirect chains)
• [ ] HSTS Enabled: Strict-Transport-Security header configured
• [ ] Modern TLS Only: TLS 1.2+ only (disable SSL and TLS 1.0/1.1)

HSTS Configuration

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

• max-age: How long browsers should remember HTTPS (1 year recommended)
• includeSubDomains: Apply to all subdomains
• preload: Submit to HSTS preload list

Security Headers

Security headers are HTTP response headers that protect against various attacks. Use a security header analyzer to check your implementation.

Essential Security Headers

Strict-Transport-Security (HSTS)

Enforces HTTPS connections and prevents man-in-the-middle attacks.

Strict-Transport-Security: max-age=31536000; includeSubDomains

X-Frame-Options / Content-Security-Policy frame-ancestors

Prevents clickjacking attacks by controlling who can embed your site.

X-Frame-Options: DENY
# or
Content-Security-Policy: frame-ancestors 'none'

X-Content-Type-Options

Prevents MIME-sniffing attacks.

X-Content-Type-Options: nosniff

Content-Security-Policy (CSP)

Restricts sources for various content types, preventing XSS attacks.

Content-Security-Policy: default-src 'self'; script-src 'self' 'unsafe-inline' https://trusted.cdn.com; style-src 'self' 'unsafe-inline'

Referrer-Policy

Controls how much referrer information is sent.

Referrer-Policy: strict-origin-when-cross-origin

Permissions-Policy (formerly Feature-Policy)

Controls browser features your site can access.

Permissions-Policy: geolocation=(self), camera=(), microphone=()

Cookie Security

Cookies are a common attack vector. Proper configuration is essential.

Secure Cookie Attributes

• [ ] Secure Flag: Cookies only sent over HTTPS
• [ ] HttpOnly Flag: JavaScript cannot access cookies (prevents XSS theft)
• [ ] SameSite Attribute: Controls cross-site request cookies
  • Strict: Best security, only same-site requests
  • Lax: Balanced security, allows top-level navigation
  • None: Required for cross-site cookies (must use Secure)
• [ ] Appropriate Expiration: Session cookies should expire appropriately

Example Secure Cookie

Set-Cookie: sessionid=abc123; Secure; HttpOnly; SameSite=Strict; Path=/; Max-Age=3600

Input Validation & XSS Prevention

Cross-site scripting (XSS) remains one of the most common web vulnerabilities.

XSS Prevention Checklist

• [ ] Output Encoding: Encode all user-generated content before display
• [ ] Content Security Policy: Restrict script sources
• [ ] Input Sanitization: Validate and sanitize on server-side
• [ ] Context-Aware Encoding: Use appropriate encoding for HTML, JS, CSS, URLs
• [ ] Template Engine Security: Use auto-escaping templates (React, Vue handle this)
• [ ] HTTPOnly Cookies: Prevent session theft via XSS

SQL Injection Prevention

• [ ] Parameterized Queries: Always use prepared statements
• [ ] ORM Usage: Use Object-Relational Mapping libraries
• [ ] Input Validation: Validate type, length, format
• [ ] Least Privilege: Database accounts with minimal permissions

// Bad: Vulnerable to SQL injection
const query = `SELECT * FROM users WHERE id = '${userInput}'`;

// Good: Parameterized query
const query = "SELECT * FROM users WHERE id = ?";
db.execute(query, [userInput]);

Third-Party Security

Third-party scripts and dependencies are a major security risk. The average website loads dozens of third-party resources.

Third-Party Risk Management

• [ ] Audit All Scripts: Know every third-party script on your site
• [ ] Use Subresource Integrity (SRI): For CDN resources
• [ ] Nonce-Based CSP: Allow only specific script versions
• [ ] Regular Updates: Keep all dependencies updated
• [ ] Vendor Security: Assess vendor security practices
• [ ] Performance Monitoring: Watch for unexpected behavior

Subresource Integrity Example

<script
  src="https://code.jquery.com/jquery-3.6.0.min.js"
  integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4="
  crossorigin="anonymous"
></script>

Access Control

Proper access control prevents unauthorized access to sensitive areas.

Authentication Security

• [ ] Rate Limiting: On login endpoints (prevent brute force)
• [ ] Account Lockout: After failed login attempts
• [ ] Multi-Factor Authentication: For admin areas
• [ ] Strong Password Policy: Enforce complexity requirements
• [ ] Secure Password Reset: Time-limited, single-use tokens
• [ ] Session Management: Proper timeout and invalidation

Authorization Checklist

• [ ] Role-Based Access Control (RBAC): Users have minimum required access
• [ ] Principle of Least Privilege: Default deny, explicit allow
• [ ] IP Whitelisting: For sensitive admin areas
• [ ] API Authentication: Proper API key/token management
• [ ] File Access Controls: Prevent directory traversal

Protection Against Common Attacks

Cross-Site Request Forgery (CSRF)

• [ ] CSRF Tokens: Include tokens on state-changing requests
• [ ] SameSite Cookies: Prevent cross-site cookie sending
• [ ] Custom Headers: Require X-Requested-With for AJAX

Authentication Attacks

• [ ] Login Rate Limiting: Prevent brute force attacks
• [ ] Secure Session Storage: Don't expose session IDs in URLs
• [ ] Logout Functionality: Complete session termination
• [ ] Remember Me Security: Use persistent, secure tokens

Monitoring & Logging

You can't secure what you can't see. Proper monitoring is essential.

Security Monitoring

• [ ] Security Event Logging: All authentication, authorization changes
• [ ] Failed Login Alerts: Notify on suspicious patterns
• [ ] File Integrity Monitoring: Alert on unexpected file changes
• [ ] Web Application Firewall (WAF): Block common attack patterns
• [ ] Uptime Monitoring: With security checks
• [ ] Error Handling: Secure error messages (don't leak information)

Regular Security Audits

Security is not a set-and-forget task. Schedule regular reviews.

Audit Schedule

| Task | Frequency | | ---------------------- | --------- | | Dependency updates | Weekly | | Security header review | Monthly | | Full security audit | Quarterly | | Penetration testing | Annually | | Access review | Quarterly |

Automated Security Scanning

Use automated tools to continuously monitor your security posture:

• [ ] Dependency Scanning: Check for vulnerable packages
• [ ] SAST: Static Application Security Testing
• [ ] DAST: Dynamic Application Security Testing
• [ ] Container Scanning: If using Docker
• [ ] Secret Scanning: Ensure no secrets in code

Quick Security Test

You can perform a basic security check right now:

1. Visit your website
2. Open browser DevTools (F12)
3. Check the Network tab for security headers
4. Look for HTTPS and valid certificate
5. Verify cookies have Secure and HttpOnly flags

For a comprehensive security analysis, run a free security scan to check your website against this entire checklist.

Conclusion

Website security requires attention to many details, but implementing this checklist will protect your site against the most common threats. Start with the essentials (HTTPS, security headers, secure cookies) and work your way through the more advanced items.

Remember: security is an ongoing process, not a destination. Regular reviews and updates are essential to maintaining a secure website in 2025 and beyond.