OWASP Top 10 2025: Most Common Security Vulnerabilities in Web Applications

OWASP (Open Web Application Security Project) Top 10 is a globally referenced standard that ranks the most critical security risks in web applications. This list defines the vulnerabilities that developers and security teams should prioritize. In this guide, we cover each risk with real-world examples and concrete prevention methods.

A01: Broken Access Control

Access control vulnerabilities rank first on the OWASP list. This category includes users accessing unauthorized resources, viewing other users' data, or executing admin functions. IDOR (Insecure Direct Object Reference) is the most common example.

// WRONG: User ID taken from URL, no verification
app.get('/api/users/:id/orders', (req, res) => {
  return db.getOrders(req.params.id); // IDOR vulnerability!
});

// CORRECT: Verify session user matches requested user
app.get('/api/users/:id/orders', auth, (req, res) => {
  if (req.user.id !== req.params.id && !req.user.isAdmin) {
    return res.status(403).json({ error: 'Forbidden' });
  }
  return db.getOrders(req.params.id);
});

A02: Cryptographic Failures and A03: Injection

Cryptographic failures include weak hash algorithms (MD5, SHA1), plaintext password storage, and insufficient TLS configuration. Injection vulnerabilities include SQL, NoSQL, OS command, and LDAP injection. Parameterized queries and input validation are the primary defense methods.

A04-A07: Design, Configuration, and Identity Risks

A04 (Insecure Design) covers neglecting security at the design phase, A05 (Security Misconfiguration) covers unchanged default configurations, A06 (Vulnerable Components) covers outdated dependencies, and A07 (Authentication Failures) covers weak authentication mechanisms.

# A05: Security configuration check
# Check for default credentials
grep -r "admin:admin" /etc/ 2>/dev/null

# A06: Scan for outdated dependencies
npm audit
pip audit
composer audit

# Check security headers
curl -I https://example.com | grep -i "x-frame\|x-content\|strict-transport"

A08-A10: Integrity, Logging, and SSRF

A08 (Software and Data Integrity Failures) covers updates from untrusted sources, A09 (Security Logging Failures) covers insufficient logging, and A10 (SSRF - Server-Side Request Forgery) covers the server making requests to internal networks. SSRF poses particular risk in cloud environments for accessing metadata endpoints.

// SSRF prevention: URL whitelist and internal network check
const allowedHosts = ['api.example.com', 'cdn.example.com'];

function isAllowedUrl(url) {
  const parsed = new URL(url);
  // Block internal network addresses
  if (parsed.hostname.match(/^(10\.|172\.(1[6-9]|2|3[01])\.|192\.168\.|127\.)/)) {
    return false;
  }
  // Block metadata endpoints
  if (parsed.hostname === '169.254.169.254') {
    return false;
  }
  return allowedHosts.includes(parsed.hostname);
}

To strengthen your web application security, check our WAF/ModSecurity guide. For server security, see our Hardening Checklist. To protect your API keys, review our Secrets Management guide. Build your secure infrastructure with Hosted Cloud cloud servers.

Frequently Asked Questions

Conclusion

The OWASP Top 10 is the fundamental reference for web application security. Adopt secure coding practices, keep your dependencies up to date, and integrate security scanning into your CI/CD pipeline to prevent risks like Broken Access Control, Injection, and SSRF.