The OWASP Top 10 is a standard awareness document that represents a broad consensus about the most critical security risks to web applications. Published by the Open Web Application Security Project (OWASP), it's updated every few years to reflect the current threat landscape.

The importance lies in:

• Industry Standard: Widely recognized benchmark for application security
• Risk Prioritization: Helps organizations focus on the most critical threats
• Developer Education: Provides guidance for secure coding practices
• Compliance: Many security frameworks reference OWASP Top 10
• Cost-Effective Security: Addresses the most common vulnerabilities that cause the majority of breaches

The current OWASP Top 10 (2021) includes risks like Broken Access Control, Cryptographic Failures, Injection, and others.

Broken Access Control occurs when restrictions on authenticated users are not properly enforced, allowing them to access unauthorized functionality or data.

Common scenarios:

• Vertical privilege escalation: Regular user accessing admin functions
• Horizontal privilege escalation: User accessing another user's data
• Missing authorization checks: Direct object references without validation

Example:

// Vulnerable URL
GET /api/user/123/profile

// Attacker changes user ID
GET /api/user/456/profile  // Accesses another user's profile

Prevention:

• Implement proper authorization checks
• Use deny-by-default principle
• Validate user permissions on every request
• Use role-based access control (RBAC)
• Log access control failures