OWASP Web and Mobile Security

Spent the last few months diving deep into OWASP guidelines for web and mobile security. Here’s what actually matters when you’re building real applications.

Web Security That Works

Input validation isn’t optional. Every single input needs validation. Not just “check if it’s a string” validation - proper validation that understands what the data should look like and rejects everything else.

SQL injection is still everywhere. Even with ORMs, you can still mess this up. Parameterized queries aren’t optional - they’re mandatory. If you’re concatenating strings into SQL queries, you’re doing it wrong.

XSS protection is harder than it looks. Content Security Policy headers help, but they’re not magic. You need to sanitize output, not just input. And no, htmlspecialchars() isn’t enough for complex applications.

Mobile Security Reality

Certificate pinning is a pain, but necessary. Yes, it breaks when certificates rotate. Yes, it’s annoying to manage. But if you’re handling sensitive data, you need it. The alternative is trusting the entire certificate chain, which is asking for trouble.

Biometric authentication isn’t bulletproof. Fingerprints can be spoofed. Face recognition can be fooled. Use biometrics as a convenience factor, not as your primary security mechanism.

App transport security matters. HTTP is dead for anything important. Use HTTPS everywhere, and make sure your app actually validates certificates properly.

The OWASP Top 10: What You Need to Know

1. Broken Access Control

The #1 vulnerability for a reason. Most developers confuse authentication with authorization. You can be logged in but still not authorized to access specific resources. Implement proper role-based access control (RBAC) and test it thoroughly.

Common mistakes:

Direct object references without proper authorization checks
Missing access controls on API endpoints
Privilege escalation through parameter manipulation

2. Cryptographic Failures

Encryption isn’t optional anymore. Use strong encryption algorithms (AES-256, RSA-2048+), proper key management, and never store sensitive data in plaintext. Your users’ data is only as secure as your weakest encryption.

What to encrypt:

Passwords (use bcrypt, scrypt, or Argon2)
Personal data (PII, financial information)
Session tokens and API keys
Data in transit (TLS 1.3)

3. Injection

SQL injection is still everywhere. Even with ORMs, you can still mess this up. Use parameterized queries everywhere, validate all inputs, and implement proper output encoding.

Types of injection:

SQL injection (most common)
NoSQL injection (MongoDB, CouchDB)
LDAP injection
Command injection
XPath injection

4. Insecure Design

Security by design, not by accident. Threat modeling, secure architecture patterns, and security requirements should be part of your design process from day one.

Design principles:

Fail securely
Defense in depth
Principle of least privilege
Separation of concerns

5. Security Misconfiguration

Default configurations are dangerous. Change default passwords, disable unnecessary services, remove debug information from production, and keep your security headers up to date.

Common misconfigurations:

Default admin passwords
Unnecessary services running
Debug information in production
Missing security headers
Outdated software versions

6. Vulnerable and Outdated Components

Your dependencies are your responsibility. Keep all components updated, scan for vulnerabilities regularly, and have a plan for when critical vulnerabilities are discovered.

Component management:

Regular vulnerability scanning
Automated dependency updates
Security patch management
License compliance

7. Identification and Authentication Failures

Authentication is hard to get right. Implement multi-factor authentication, strong password policies, account lockout mechanisms, and session management.

Authentication best practices:

Multi-factor authentication (MFA)
Strong password policies
Account lockout after failed attempts
Secure session management
Password reset mechanisms

8. Software and Data Integrity Failures

Trust but verify. Implement code signing, secure update mechanisms, and integrity checks for critical data.

Integrity controls:

Code signing and verification
Secure update mechanisms
Data integrity checks
Supply chain security

9. Security Logging and Monitoring Failures

You can’t secure what you can’t see. Implement comprehensive logging, real-time monitoring, and incident response procedures.

Logging requirements:

Authentication events
Authorization failures
Data access and modification
System errors and exceptions
Security events

10. Server-Side Request Forgery (SSRF)

Don’t trust user input for network requests. Validate and sanitize all URLs, implement allowlists for internal resources, and use network segmentation.

SSRF prevention:

URL validation and sanitization
Allowlists for internal resources
Network segmentation
Input validation

What Actually Works

Start with threat modeling. Figure out what you’re actually protecting and who might want to attack it. Most security problems come from not understanding the threat landscape.

Security testing isn’t optional. Automated scanning, manual testing, penetration testing - you need all of it. And you need to do it regularly, not just before launch.

Incident response planning saves companies. When something goes wrong (and it will), you need a plan. Who do you call? What do you do? How do you communicate with users?

The Bottom Line

Security isn’t a feature you add at the end. It’s something you build in from the beginning. The OWASP guidelines are a good starting point, but they’re not a checklist - they’re a framework for thinking about security systematically.

Most security failures come from not taking the basics seriously. Get the fundamentals right, and you’ll be ahead of 90% of applications out there.

Need help with security implementation? Contact us for a security assessment of your web or mobile application.