OWASP Top 10 Security Vulnerabilities Explained (2024 Edition)

The OWASP Top 10 is the definitive list of the most critical web application security risks. Understanding these vulnerabilities is essential for anyone building or maintaining websites.

This guide breaks down each vulnerability with real-world examples and practical solutions.

What is OWASP?

The Open Web Application Security Project (OWASP) is a nonprofit foundation dedicated to improving software security. Their Top 10 list is updated every 3-4 years based on real vulnerability data from hundreds of organizations.

OWASP Top 10 (2021

Current)

1. Broken Access Control

Risk Level: CRITICAL

What it is: Users can access resources or perform actions they shouldn't be authorized for.

Real-world example:

Changing URL parameter from `/user/profile?id=123` to `id=124` to view another user's profile

Accessing admin panels without proper authentication

Modifying API requests to escalate privileges

How to prevent:
✅ Deny by default (require explicit permissions)
✅ Enforce server-side access control checks
✅ Never rely on client-side validation alone
✅ Implement proper session management
✅ Log access control failures

Code example (secure):
```javascript
// Server-side check
if (currentUser.id !== requestedUserId && !currentUser.isAdmin) {
return res.status(403).json({ error: 'Unauthorized' });
}
```

2. Cryptographic Failures

Risk Level: CRITICAL

What it is: Sensitive data exposed due to weak or missing encryption.

Common failures:

Storing passwords in plaintext

Using outdated encryption algorithms (MD5, SHA1)

Transmitting sensitive data over HTTP

Hard-coding encryption keys in source code

How to prevent:
✅ Use HTTPS everywhere (TLS 1.3)
✅ Hash passwords with bcrypt, Argon2, or scrypt
✅ Encrypt sensitive data at rest (AES-256)
✅ Use secure random number generators
✅ Implement proper key management

Example:
```javascript
// ❌ BAD
const password = req.body.password;
users.create({ password: password });

// ✅ GOOD
const bcrypt = require('bcrypt');
const hashedPassword = await bcrypt.hash(req.body.password, 12);
users.create({ password: hashedPassword });
```

3. Injection

Risk Level: HIGH

What it is: Untrusted data sent to an interpreter as part of a command or query.

Types:

SQL injection

NoSQL injection

OS command injection

LDAP injection

SQL Injection example:
```sql
-

❌ Vulnerable
SELECT * FROM users WHERE username = '$username' AND password = '$password'

-

Attacker input: ' OR '1'='1
-

Result: SELECT * FROM users WHERE username = '' OR '1'='1' AND password = ''
-

Bypasses authentication!
```

How to prevent:
✅ Use parameterized queries (prepared statements)
✅ Use ORM frameworks properly
✅ Validate and sanitize all inputs
✅ Use least-privilege database accounts
✅ Implement WAF rules

Secure code:
```javascript
// ✅ Using parameterized query
const query = 'SELECT * FROM users WHERE username = ? AND password = ?';
db.execute(query, [username, password]);
```

4. Insecure Design

Risk Level: HIGH

What it is: Missing or ineffective security controls due to flawed design.

Examples:

No rate limiting on password reset (account takeover)

Unlimited file uploads (DoS)

No transaction limits (fraud)

Missing security requirements in planning phase

How to prevent:
✅ Include security in design phase
✅ Implement threat modeling
✅ Use secure design patterns
✅ Apply principle of least privilege
✅ Separate sensitive operations

5. Security Misconfiguration

Risk Level: HIGH

What it is: Incorrectly configured security settings leaving vulnerabilities.

Common issues:

Default credentials still enabled

Unnecessary features enabled

Error messages revealing system details

Missing security patches

Insecure cloud storage permissions

Examples:

Admin/admin credentials

Directory listing enabled

Stack traces visible to users

Debug mode in production

How to prevent:
✅ Implement hardening procedures
✅ Remove unused features/accounts
✅ Keep all software updated
✅ Use security headers
✅ Regular security reviews

6. Vulnerable and Outdated Components

Risk Level: HIGH

What it is: Using libraries, frameworks, or software with known vulnerabilities.

Real impact:

2017 Equifax breach: Unpatched Apache Struts (143M records exposed)

Log4Shell (2021): Affected millions of applications worldwide

How to prevent:
✅ Inventory all dependencies
✅ Monitor vulnerability databases (CVE, NVD)
✅ Use dependency scanning tools (Snyk, Dependabot)
✅ Update regularly (but test first!)
✅ Remove unused dependencies

Tools:

`npm audit` (Node.js)

Snyk

OWASP Dependency-Check

7. Identification and Authentication Failures

Risk Level: HIGH

What it is: Broken authentication allowing attackers to compromise accounts.

Common weaknesses:

Permits brute force attacks

Permits default/weak passwords

Missing or ineffective MFA

Session IDs in URLs

Session fixation vulnerabilities

How to prevent:
✅ Implement multi-factor authentication
✅ Never ship with default credentials
✅ Enforce strong password policies
✅ Rate-limit login attempts
✅ Use secure session management
✅ Implement account lockout after failed attempts

Best practices:

Password minimum: 12 characters

Require complexity (upper, lower, numbers, symbols)

Check against common password lists

Implement CAPTCHA after failures

8. Software and Data Integrity Failures

Risk Level: MEDIUM

What it is: Code and infrastructure without protection against integrity violations.

Examples:

Auto-updates without signature verification

Insecure CI/CD pipelines

Untrusted CDN sources

Deserialization of untrusted data

How to prevent:
✅ Use digital signatures for updates
✅ Verify integrity with checksums (SHA-256)
✅ Use trusted repositories only
✅ Implement Subresource Integrity (SRI)
✅ Review third-party code

SRI Example:
```html

```

9. Security Logging and Monitoring Failures

Risk Level: MEDIUM

What it is: Insufficient logging allowing attacks to go undetected.

Statistics: Average time to detect a breach: 207 days (IBM 2023)

What to log:
✅ Login attempts (success and failure)
✅ Access control failures
✅ Server-side input validation failures
✅ Authentication token failures

How to prevent:
✅ Log all security-relevant events
✅ Ensure logs are tamper-proof
✅ Implement real-time monitoring
✅ Set up alerts for suspicious patterns
✅ Regular log reviews

⚠️ Never log:
❌ Passwords
❌ Session tokens
❌ Credit card numbers
❌ Personal health information

10. Server-Side Request Forgery (SSRF)

Risk Level: MEDIUM

What it is: Web application fetching remote resources without validating user-supplied URLs.

Attack scenario:
```
// Attacker supplies: http://localhost:22/admin
app.get('/fetch', (req, res) => {
const url = req.query.url;
fetch(url).then(data => res.send(data)); // ❌ Dangerous!
});
```

How to prevent:
✅ Whitelist allowed destinations
✅ Disable HTTP redirections
✅ Use network segmentation
✅ Validate and sanitize all URLs
✅ Implement deny by default

OWASP Top 10 Quick Reference

| Vulnerability | Risk | Prevention Priority |
|---|---|---|
| Broken Access Control | CRITICAL | HIGHEST |
| Cryptographic Failures | CRITICAL | HIGHEST |
| Injection | HIGH | HIGH |
| Insecure Design | HIGH | HIGH |
| Security Misconfiguration | HIGH | HIGH |
| Vulnerable Components | HIGH | HIGH |
| Auth Failures | HIGH | HIGH |
| Integrity Failures | MEDIUM | MEDIUM |
| Logging Failures | MEDIUM | MEDIUM |
| SSRF | MEDIUM | MEDIUM |

Implementing OWASP Protection

Development Phase
1. Security training for developers
2. Secure coding standards
3. Code review checklist based on OWASP
4. Static analysis tools (SAST)

Testing Phase
1. Dynamic analysis (DAST)
2. Penetration testing
3. Vulnerability scanning
4. Security regression testing

Production Phase
1. Web Application Firewall (WAF)
2. Runtime protection (RASP)
3. Continuous monitoring
4. Incident response plan

Tools for OWASP Compliance

Free tools:

OWASP ZAP (vulnerability scanner)

Burp Suite Community

SQLMap (SQL injection testing)

Nikto (web server scanner)

Commercial tools:

Snyk

Checkmarx

Veracode

Acunetix

Conclusion

The OWASP Top 10 provides a roadmap for securing web applications. Focus on the CRITICAL and HIGH-risk vulnerabilities first, then systematically address the remaining items.

Remember:

Security is a process, not a product

Defense in depth (multiple layers)

Assume breach (plan for it)

Keep learning (threats evolve)

Security Wiz OWASP Protection

We build OWASP Top 10 protections into every website from day one:

✅ Secure authentication & authorization
✅ Input validation & sanitization
✅ Encryption (transit & rest)
✅ Security headers
✅ Regular dependency updates
✅ Comprehensive logging
✅ WAF protection
✅ Continuous monitoring

Ready to build securely? [Get started](#contact) with OWASP-compliant development.

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Resources:

[Official OWASP Top 10](https://owasp.org/Top10/)

[OWASP Cheat Sheet Series](https://cheatsheetseries.owasp.org/)

[OWASP Testing Guide](https://owasp.org/www-project-web-security-testing-guide/)