Cybersecurity Vulnerability API Testing API Security

What is API security testing?

Pallavi Vishwakarma

Member of Technical staff

Oct 11 2022

3 min reading

Figure 1

API stands for Application Programming Interface it allows applications to communicate with one another. APIs are being increasingly leveraged, yet they are less secure and more exposed. It is the most important part of an application as whenever there is a web request APIs are invoked and it incorporates your methods, headers, and other parameters. Therefore, as data flows through them it is essential to secure APIs to prevent data leakage.


API security testing is the process of testing APIs to find out the vulnerabilities, security misconfiguration, and any potential security gaps for the technical team to fix. It requires to be tested throughout its development lifecycle as it will ensure that API operates as intended and is limited to those tasks and it will sec.


Why API security testing is important?

  • Today, the most valuable thing is data and as APIs connect the most sensitive data it becomes the easiest point for attackers who want to access your data.
  • If there is an error/bug in your API, every application that uses an API is impacted including any third parties accessing your API.
  • APIs have documentation that can be used by attackers as a blueprint.
  • A vulnerable API can lead to Sanctioning fuzzy inputs, Injection vulnerabilities, parameters tempering, Unauthorized access, etc.
  • APIs expose application logic and data, which puts you and your company at risk as it provides access to many sources of potentially sensitive data and mission-critical services.
  • APIs can increase the application attack surface.

An annual research report states that 35% of analyzed web applications had APIs misuse issues and that increased to 52% for mobile applications so understanding APIs vulnerabilities and weaknesses will help you gain a comprehensive view of the potential attack vectors that could be used to breach an application.


Top 10 OWASP API vulnerabilities (2019):

  1. Broken object level Authorization
  2. Broken User Authentication
  3. Excessive data exposure
  4. Lack of Resources & Rate Limiting
  5. Broken function level authorization
  6. Mass Assignment
  7. Security Misconfiguration
  8. Injection
  9. Improper Assets Management
  10. Insufficient Loggin & Monitoring

Types of API security tests:

  • Fuzz testing: Fuzzing is the process of feeding the API with erroneous or invalid unexpected data to the API to check whether it can spill some information, some error messages, or anything to imply that random data has been processed by the API.


  • SQLi testing: Testing the API for SQL injection attack to check whether the API process any unsanitized input from the database. It mostly happens when API cannot simply distinguish between code and untrusted user data.
  • Test API for parameter tempering: Parameter tempering occurs when there is a hidden or fixed field present the attacker can manipulate the fields and modify the application data. For example, by tempering the parameter the attacker can alter the product’s value and essentially get it for free.
  • Functional testing: It means checking API function against particular circumstances to ensure expected outcomes.
  • Testing for unhandled HTTP methods: When an API communicates with a web application it sends an HTTP request but sometimes that HTTP is not supported by the web application and mostly it should be through an error but for some vulnerable APIs it is not the case so it's essential to test API against such HTTP methods.

Benefits of API security testing:

  • API security testing aids in the detection and avoidance of vulnerabilities and the potential organizational risk they pose.
  • Finding areas where an API deviates from published API guidelines can also be accomplished with the aid of API security testing.
  • Analytics for security compliance and reporting that provide a real-time understanding of risks related to your APIs.
  • API security testing does not depend on technology as it focuses on HTTP requests and responses which allows testers to use any language to test the APIs reducing the company testing cost.


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