Vulnerabilities Lurk in Every Endpoint
APIs are the central nervous system of modern applications. They process your most valuable data, but are often a blind spot in your security strategy. The most common and critical vulnerabilities are not obvious, but hidden deep within the logic of the endpoints.
Broken Object Level Authorization (BOLA)
The most common API vulnerability: An authenticated user manipulates an ID in the request (e.g., an order or user ID) and can thus view, change or delete other users’ data. A catastrophic scenario for any data-driven business.
Weak Authentication
Whether it’s incorrectly validated JWTs (JSON Web Tokens), weak API keys or access tokens that never expire – if authentication can be bypassed at just one endpoint, the entire infrastructure is often open to unauthorised access.
Hidden Data Leaks
Your app may only display the user name, but the API endpoint provides the complete user object structure in the background, including password hash, address and internal notes. Such hidden data leaks (excessive data exposure) are a gold mine for attackers.
Our audit approach for your API security
An API is not a web page. Its security requires a specialised, in-depth approach that goes beyond traditional web testing. We focus on the unique vulnerabilities and architectures that characterise modern APIs.
Analysis using OWASP API Security Top 10
The industry standard for API security forms the basis of our work. We systematically check your API for all critical risks defined in the OWASP API Security Top 10. Our focus is on the vulnerabilities with the greatest potential for damage.
- Checking for insufficient object authorisation at property and instance level (BOLA/BOPLA).
- Analysis of authentication mechanisms, in particular JWTs, OAuth 2.0 and API keys.
- Detection of excessive data exposure and mass assignment vulnerabilities.
- Identification of rate limiting and resource management errors.
- Search for classic and novel injection vulnerabilities within API requests.
Manual analysis meets specialised tools
We don’t rely on automated scans alone. Our experts use the same tools as your developers (e.g. Postman, Insomnia) as well as specialised security software (e.g. Burp Suite) to manually dissect the logic of your API thoroughly.
- Manual examination of business logic and endpoint interactions.
- Intelligent fuzzing of parameters and request bodies to uncover edge cases.
- Analysis of your API documentation (Swagger/OpenAPI) for conceptual design weaknesses.
- Systematic attempts to bypass authentication and authorisation schemes.
A dedicated API test is a critical part of our comprehensive security analyses.
→ Find out more about our penetration tests and the different types of tests on our main page.
In Practice
From Compliance Risk to Enterprise-Ready Seal
Challenge:
A fintech service provider had to meet the strict security requirements of the DORA Act for its corporate customers. An independent security audit of its central banking API was not an option, but a mandatory requirement in order to operate in the regulated financial market.
Solution:
Lutra Security was commissioned to perform a targeted gray-box API penetration test. The focus was on the most critical risks of the OWASP API Security Top 10, in particular the circumvention of authentication and authorisation logic to simulate unauthorised transactions or data access.
Result:
Our analysis identified critical vulnerabilities, including a faulty implementation of rights checking that would have allowed unauthorised access to third-party account data. With our detailed report, the gaps were closed. The final test report served as decisive proof of security to meet DORA requirements and successfully bring the first major customers from the financial sector on board.
Our work is based on recognised standards
A web penetration test focuses on the user interface (UI) and user interactions, such as cross-site scripting (XSS). An API penetration test, on the other hand, targets the technical backbone of your application directly. Here, we analyse the core business logic, data and rights management directly at the endpoints, where the most critical vulnerabilities (such as those from the OWASP API Security Top 10) are often found.
Up-to-date API documentation (e.g. a Swagger or OpenAPI specification) is extremely helpful and makes testing more efficient, as we know all endpoints and their parameters from the start (white box approach). If no documentation is available, we can work using a black box approach and explore the API structure ourselves by analysing the application that uses it.
Yes, we have specialised in the specific security risks of both architectures. While we check endpoint enumeration and HTTP method security, among other things, for REST APIs, we focus on the unique risks of GraphQL interfaces, such as insecure introspection queries, complex queries that can lead to denial of service, and permission issues in nested resolvers.
Yes, absolutely. The security of internal APIs is particularly crucial, as they are often the target of attackers who have already gained initial access to the network (lateral movement). Checking your internal API communication, for example in microservice architectures, is a central component of a comprehensive security strategy.
Ready to put your API to the test?
Contact us for a free, non-committal initial consultation, during which we will analyse your requirements:
Founded by experts. Driven by your safety.
We are not an anonymous agency. Lutra Security was founded by four IT security experts with a shared mission: to proactively protect companies and make complex security solutions understandable and accessible. Your security is personally guaranteed by the founders.
David Schneider
Emanuel Böse
Konstantin Weddige
