Mobile applications and APIs power most modern digital services, which makes them prime targets for attackers. As organizations adopt mobile-first and API-driven architectures, security teams need professionals who understand mobile app security, API pentesting, and OAuth security in depth. Interviews for modern pentesting roles focus on real attack scenarios, authentication flows, data exposure, and business logic flaws. This blog covers practical mobile pentesting interview and API pentesting questions with clear answers to help you prepare for real-world security interviews and offensive security roles.
Interview Questions and Answers
Question 1. What is mobile application pentesting?
Answer: Mobile application pentesting is the process of testing mobile apps for security weaknesses such as insecure storage, weak authentication, improper encryption, and insecure API communication. The goal is to identify vulnerabilities that could lead to data leakage or unauthorized access.
Question 2. What are the main differences between mobile pentesting and web pentesting?
Answer: Mobile pentesting involves analyzing application binaries, local storage, and device-level security, while web pentesting focuses mainly on server-side logic. Mobile apps often rely heavily on APIs, making API pentesting a critical part of mobile app security.
Question 3. What platforms are commonly tested during mobile pentesting?
Answer: Mobile pentesting typically covers Android and iOS platforms. Each platform has different security mechanisms, storage methods, and permission models that must be tested separately.
Question 4. What is API pentesting?
Answer: API pentesting focuses on testing backend services exposed through APIs for vulnerabilities such as broken authentication, improper authorization, data exposure, and business logic flaws. APIs often serve mobile and web clients, making them high-value attack targets.
Question 5. Why is API pentesting critical in modern pentesting?
Answer: Modern applications rely on APIs for authentication, data exchange, and business operations. A single vulnerable API can expose large amounts of sensitive data even if the frontend appears secure.
Question 6. What is OAuth and why is OAuth security important?
Answer: OAuth is an authorization framework that allows applications to access resources on behalf of users. OAuth security is important because misconfigurations can allow token theft, unauthorized access, or privilege escalation.
Question 7. Real scenario: How would you test an OAuth implementation?
Answer: I would analyze token generation, token expiration, scope enforcement, and refresh token handling. I would attempt token reuse, scope manipulation, and access resources with expired or tampered tokens to validate authorization controls.
Question 8. What are common mobile app security issues?
Answer: Common issues include insecure local storage, hardcoded secrets, improper certificate validation, weak encryption, and excessive permissions. These issues can expose sensitive user data or enable reverse engineering.
Question 9. Real scenario: How do you test insecure local storage on a mobile app?
Answer: I would inspect application storage files, databases, and shared preferences to check if sensitive data such as tokens or credentials are stored in plain text or weakly encrypted.
Question 10. What is certificate pinning and how does it affect pentesting?
Answer: Certificate pinning ensures the app only trusts specific certificates. While it improves security, pentesters may need to bypass pinning during testing to inspect encrypted traffic and analyze API communication.
Question 11. How do you analyze API requests during mobile pentesting?
Answer: I intercept mobile traffic using a proxy tool and analyze API endpoints, request parameters, authentication headers, and responses. This helps identify authorization flaws, data leakage, and logic issues.
Question 12. What is broken object level authorization?
Answer: Broken object level authorization occurs when APIs fail to properly verify whether a user is allowed to access a specific object. Attackers can manipulate object identifiers to access unauthorized data.
Question 13. Real scenario: How would you exploit a broken authorization issue in an API?
Answer: I would change object IDs or user identifiers in API requests. If the API returns data belonging to another user without proper checks, it confirms an authorization vulnerability.
Question 14. What is rate limiting and why is it important for API security?
Answer: Rate limiting restricts the number of requests a client can make. Without rate limiting, APIs are vulnerable to brute-force attacks, credential stuffing, and denial-of-service attempts.
Question 15. How do you test for business logic flaws in APIs?
Answer: I analyze workflows such as payment processing, order management, or account updates. I test unexpected sequences, repeated requests, and missing validations that could lead to financial or data abuse.
Question 16. What role does mobile app reverse engineering play in pentesting?
Answer: Reverse engineering helps understand application logic, API endpoints, and hidden functionality. It can reveal hardcoded secrets, debug flags, or undocumented API calls.
Question 17. What are common authentication issues found in mobile APIs?
Answer: Issues include token reuse, missing token expiration, weak session handling, and reliance on client-side checks. These weaknesses can lead to account takeover or privilege escalation.
Question 18. Real scenario: How would you test token-based authentication?
Answer: I would test token expiration, reuse tokens across accounts, manipulate token values, and attempt access after logout to verify proper session invalidation.
Question 19. How does mobile app security differ in modern architectures?
Answer: Modern architectures rely heavily on microservices and APIs. Security shifts from client-side controls to backend enforcement, making API pentesting and OAuth security more critical than UI testing.
Question 20. What is the importance of reporting in mobile and API pentesting?
Answer: Reporting explains technical findings in a way that developers and stakeholders understand. It includes risk impact, reproduction steps, and remediation guidance to improve overall security.
Conclusion
Mobile and API pentesting interviews focus on real-world attack scenarios, modern application architecture, and secure authentication mechanisms. Understanding mobile app security, API pentesting techniques, OAuth security, and business logic flaws is essential for modern pentesting roles. Candidates who can clearly explain vulnerabilities, demonstrate structured testing approaches, and communicate risk effectively stand out in mobile pentesting interviews and offensive security roles.
