API Penetration Testing

What Is API Penetration Testing?

API Penetration Testing is a focused security assessment that targets your application's backend interfaces. These interfaces often expose sensitive data and functionality, making them prime targets for attackers.

• Test authentication, token validation, and session management
• Check authorization for each API method and resource
• Identify input validation, injection, and serialization flaws
• Audit rate-limiting and abuse-prevention mechanisms

Our tests are guided by the OWASP API Top 10, real-world attack techniques, and fuzzing tools.

What Do We Test?

• Broken Object Level Authorization (BOLA)
• Mass assignment and parameter pollution
• Token and key leakage in headers or URLs
• Insecure data serialization and deserialization
• Improper asset exposure via OpenAPI/Swagger
• Rate-limiting and abuse-resistance
• Business logic abuse scenarios

Why It’s Critical

APIs often bypass traditional web protections and are less visible to security teams—making them a favored entry point for attackers.

• Catch flaws missed by static scanners
• Prevent abuse of exposed backend functionality
• Achieve compliance with PCI DSS, HIPAA, SOC2, and ISO standards
• Build customer trust through secure development practices

Our Testing Approach

We approach API testing with a methodology that blends automated tools, manual analysis, and protocol level understanding. Tools like Burp Suite, Postman are used to explore and test each endpoint in detail. Our process begins with documentation review (such as Swagger/OpenAPI specs, Postman collections, or developer portals) when available. When not, we manually map the API by observing frontend interactions and inspecting network traffic to identify endpoints, parameters, authentication flows, and response structures. Next, we probe the API for vulnerabilities such as broken object-level authorization (BOLA), improper input validation, insecure authentication flows, rate limiting issues, and sensitive data exposure.

We pay special attention to IDOR risks, roleb ased access control enforcement, and business logic flaws. We don't just test what’s visible we look for undocumented endpoints, misconfigured HTTP methods, and inconsistencies between client-side expectations and server-side behavior.

Where possible, we emulate real attacker techniques to demonstrate potential impact. Ultimately, our goal is to uncover hidden flaws before attackers do, ensuring your APIs are secure, resilient, and properly hardened for real-world threats.

Real World Examples

In a SaaS API audit, our team uncovered an Insecure Direct Object Reference (IDOR) vulnerability that allowed users to enumerate and download invoices belonging to other customers through manipulation of the invoice ID in the API endpoint.

This exposed sensitive financial data and highlighted the lack of proper authorization checks on object-level access. Had an attacker discovered this vulnerability, it could have had serious consequences for the application owner, including data breaches, loss of customer trust, and potential legal or regulatory repercussions.

Engagement Process

1. Scoping & Quotation: Drop us an email, and we’ll either arrange a scoping call or send over our scoping forms. Based on the information you provide, we’ll prepare a quote for the work. Once everything is agreed upon, we’ll send through the necessary paperwork and agreements, and then schedule the assessment.
2. Assessment Phase: On the scheduled day, our team begins testing. If we detect any critical or high risk vulnerabilities during the assessment, we alert you immediately to help you respond quickly.
3. Results & Reporting: You’ll receive a professionally written report detailing each vulnerability, its business impact, technical detail, and precise guidance for remediation.
4. Free Retesting: Once you’ve resolved the major findings, we offer complimentary retesting for high and critical issues—so you can close the loop with confidence.