Complete Guide to OWASP Top 10 Web Security Vulnerabilities

The OWASP Top 10 represents the most critical security risks to web applications. Understanding these vulnerabilities is essential for any developer or security professional.

1. Broken Access Control

Access control enforces policy such that users cannot act outside of their intended permissions. Failures typically lead to unauthorized information disclosure, modification, or destruction of data.

Prevention:

• Implement proper authorization checks on every function
• Deny access by default
• Use attribute-based or role-based access control
• Disable directory listing on web servers
• Log access control failures and alert admins when appropriate

2. Cryptographic Failures

Previously known as Sensitive Data Exposure, this category focuses on failures related to cryptography which often leads to sensitive data exposure.

Prevention:

• Classify data processed, stored, or transmitted by the application
• Encrypt all sensitive data at rest and in transit
• Use up-to-date and strong standard algorithms, protocols, and keys
• Disable caching for responses containing sensitive data
• Apply required security controls as per data classification

3. Injection

Injection flaws occur when untrusted data is sent to an interpreter as part of a command or query. SQL, NoSQL, OS, and LDAP injection are common examples.

Prevention:

• Use parameterized queries (prepared statements)
• Implement input validation with whitelist approach
• Escape special characters using the specific escape syntax for that interpreter
• Use LIMIT and other SQL controls within queries to prevent mass disclosure

4. Insecure Design

A new category for 2021 focuses on risks related to design and architectural flaws, calling for more use of threat modeling, secure design patterns, and reference architectures.

Prevention:

• Establish and use a secure development lifecycle
• Use threat modeling for critical authentication, access control, business logic, and key flows
• Integrate security language and controls into user stories
• Limit resource consumption by user or service

5. Security Misconfiguration

This category includes missing security hardening across any part of the application stack, unnecessarily enabled features, or weak security settings.

Prevention:

• Implement a repeatable hardening process
• Remove or do not install unused features and frameworks
• Review and update security configurations
• Implement proper segmentation between components or tenants
• Send security directives to clients (e.g., Security Headers)

Key Takeaways

• Stay Updated: The OWASP Top 10 evolves based on emerging threats
• Defense in Depth: Implement multiple layers of security controls
• Security Training: Ensure your team understands these vulnerabilities
• Regular Testing: Conduct security assessments throughout the SDLC

Understanding and addressing these vulnerabilities is not optional—it's a fundamental requirement for building secure web applications.