OWASP API Security Top 10 Interview Questions and Answers (15 Must-Know Questions)

Master the OWASP API Security Top 10 with 15 interview questions and answers. Learn the latest API security risks, prevention techniques, Spring Boot implementation, enterprise use cases, common mistakes, and best practices.

Introduction

APIs are the backbone of modern software systems. Mobile applications, web applications, cloud services, AI platforms, IoT devices, and microservices all communicate through APIs. As APIs have become the primary entry point into enterprise systems, they have also become one of the most attractive targets for attackers.

The OWASP API Security Top 10 identifies the most critical API security risks and provides guidance for building secure APIs. These risks help organizations prioritize security controls and reduce vulnerabilities before deployment.

Understanding these risks is essential for Java Developers, Spring Boot Developers, Full Stack Engineers, DevOps Engineers, Cloud Engineers, Solution Architects, and Security Engineers.

What You'll Learn

What is OWASP?
What is the OWASP API Security Top 10?
Latest API security risks
Broken Object Level Authorization (BOLA)
Authentication and Authorization risks
Injection attacks
Security misconfiguration
API Gateway security
Spring Boot security
Enterprise best practices

API Security Architecture

                Internet
                    │
                    ▼
              Web Application
                    │
                    ▼
               API Gateway
                    │
      Authentication (OAuth2/JWT)
                    │
      Authorization (RBAC/ABAC)
                    │
         Input Validation
                    │
      Rate Limiting & WAF
                    │
                    ▼
          Spring Boot APIs
                    │
                    ▼
              Database

OWASP API Security Lifecycle

Client

↓

Authentication

↓

Authorization

↓

Validation

↓

Business Logic

↓

Database

↓

Logging

↓

Monitoring

1. What is OWASP?

Answer

OWASP (Open Worldwide Application Security Project) is a nonprofit organization that provides free resources, standards, tools, and best practices for improving software security.

Popular OWASP projects include:

OWASP Top 10
OWASP API Security Top 10
OWASP ASVS
OWASP Dependency Check
OWASP ZAP
OWASP Cheat Sheets

2. What is the OWASP API Security Top 10?

Answer

It is a list of the most critical API security risks identified by security experts based on real-world vulnerabilities and attack patterns.

Its purpose is to help developers:

Build secure APIs
Prevent data breaches
Improve secure coding practices
Meet compliance requirements

3. What is Broken Object Level Authorization (BOLA)?

Answer

BOLA occurs when an API allows users to access resources belonging to other users because object-level authorization checks are missing.

Example

User A

GET /accounts/1001

↓

Changes URL

↓

GET /accounts/1002

↓

Should Return

403 Forbidden

Prevention

Validate object ownership
Implement authorization checks on every request
Never trust client-supplied IDs

4. What is Broken Authentication?

Answer

Broken Authentication occurs when attackers can impersonate legitimate users due to weak authentication mechanisms.

Examples

Weak passwords
Stolen JWT tokens
Session hijacking
Missing MFA
Poor token validation

Prevention

OAuth2
OpenID Connect
Multi-Factor Authentication
Short-lived JWTs
Secure password storage

5. What is Broken Object Property Level Authorization?

Answer

This vulnerability occurs when users can read or modify sensitive object properties that they should not have access to.

Example

{
  "name":"John",
  "salary":95000,
  "role":"ADMIN"
}

Regular users should never receive administrative or confidential fields.

Prevention

DTOs
Field-level authorization
Response filtering

6. What is Unrestricted Resource Consumption?

Answer

APIs can become unavailable when excessive requests consume CPU, memory, bandwidth, or database resources.

Examples

Infinite pagination
Large file uploads
Expensive database queries
Bot attacks

Prevention

Rate limiting
Pagination
Request size limits
API quotas

7. What is Broken Function Level Authorization?

Answer

Users gain access to administrative functions due to missing role validation.

Example

User Role

↓

Calls

/admin/deleteUser

↓

Should Return

403 Forbidden

Prevention

Role-Based Access Control (RBAC)
Method-level security
API Gateway authorization

8. What is Unrestricted Access to Sensitive Business Flows?

Answer

Attackers abuse legitimate business operations by automating requests.

Examples

Ticket booking bots
Flash sale abuse
OTP request flooding
Payment abuse

Prevention

CAPTCHA
Rate limiting
Fraud detection
Behavioral analytics

9. What is Server-Side Request Forgery (SSRF)?

Answer

SSRF occurs when attackers force a server to make requests to internal or external systems.

Example

Attacker

↓

Image URL

↓

Internal Metadata Server

↓

Sensitive Information

Prevention

Allowlists
URL validation
Disable unnecessary outbound requests
Network segmentation

10. What is Security Misconfiguration?

Answer

Security Misconfiguration occurs when applications expose unnecessary functionality or insecure defaults.

Examples

Debug mode enabled
Default passwords
Open management endpoints
Weak TLS configuration
Directory listing enabled

Prevention

Secure defaults
Configuration reviews
Automated security scanning
Infrastructure as Code

11. What is Improper Inventory Management?

Answer

Organizations often expose forgotten, deprecated, or undocumented APIs.

Examples

Old API versions
Test endpoints
Shadow APIs
Unused admin endpoints

Prevention

API inventory
API version management
API documentation
Regular audits

12. What is Unsafe Consumption of APIs?

Answer

Applications often trust third-party APIs without validation.

Examples

Third-party payment APIs
AI APIs
Weather APIs
Banking integrations

Prevention

Validate responses
Verify certificates
Timeouts
Retry policies
Circuit breakers

13. How Can Spring Boot Prevent OWASP API Risks?

Answer

Spring Boot provides multiple security features.

Example

@Configuration
public class SecurityConfig {

    @Bean
    SecurityFilterChain security(HttpSecurity http)
            throws Exception {

        http
          .authorizeHttpRequests(auth ->
             auth.anyRequest().authenticated())
          .oauth2ResourceServer(
             oauth -> oauth.jwt());

        return http.build();
    }
}

Additional protection includes:

Bean Validation
Spring Security
Method Security
CSRF protection (for browser applications)
Exception handling
Secure headers

14. What are Common OWASP API Security Mistakes?

Answer

Common mistakes include:

Missing authorization
Hardcoded secrets
Logging JWT tokens
Weak password policies
Missing HTTPS
SQL Injection
Excessive data exposure
No rate limiting
Public management endpoints
Missing API monitoring

15. What are OWASP API Security Best Practices?

Answer

Recommended practices:

Always use HTTPS
Implement OAuth2 and JWT
Validate every request
Enforce authorization checks
Apply least privilege
Encrypt sensitive data
Enable rate limiting
Use API Gateways
Monitor API traffic
Perform regular security testing
Follow secure coding standards
Keep dependencies updated

OWASP API Security Top 10 Summary

Risk	Description
BOLA	Missing object-level authorization
Broken Authentication	Weak identity verification
Broken Object Property Authorization	Sensitive field exposure
Unrestricted Resource Consumption	Resource exhaustion
Broken Function Level Authorization	Unauthorized function access
Unrestricted Business Flows	Business logic abuse
SSRF	Server-side request attacks
Security Misconfiguration	Insecure configuration
Improper Inventory Management	Forgotten APIs
Unsafe API Consumption	Trusting external APIs

Interview Tips

Explain that OWASP provides security best practices, not security software.
Mention that the API Top 10 focuses specifically on API vulnerabilities.
Clearly differentiate authentication and authorization risks.
Explain Broken Object Level Authorization with a real-world example.
Discuss rate limiting for resource protection.
Explain SSRF with cloud metadata server examples.
Mention API Gateway responsibilities.
Discuss secure coding with Spring Security.
Highlight monitoring and logging as essential security controls.
Use banking, healthcare, and e-commerce APIs as enterprise examples.

Key Takeaways

OWASP API Security Top 10 identifies the most critical API security risks.
Broken Object Level Authorization (BOLA) is one of the most common and severe API vulnerabilities.
Strong authentication and authorization are fundamental to secure API design.
Rate limiting and resource controls help prevent denial-of-service and abuse.
API Gateways centralize authentication, authorization, throttling, and monitoring.
Spring Boot and Spring Security provide built-in mechanisms for securing REST APIs.
Regular security testing, dependency updates, and configuration reviews reduce vulnerabilities.
Organizations should maintain an inventory of all APIs and retire unused endpoints.
Secure API development requires defense in depth across identity, transport, validation, monitoring, and infrastructure.
OWASP API Security is a high-priority topic for Java, Spring Boot, Cloud, DevOps, API Security, and Solution Architect interviews.