Current Date :June 15, 2024
API Security Testing: Rules And Checklist

API Security Testing: Rules And Checklist

One of the most important assets of an organization is data.  It is essential for an organization to recognize the threats to secure data from any sort of risk.

That’s why API security testing is very necessary. An Application Programming Interface presents the easiest access point to hackers.

To get your data safe from hackers, you should utilize API security testing and assure that the API is as safe as possible. If there is an error in API, it will influence all the applications that depend upon API.

An API is a user interface designed for various users. It is made for a machine operating software so that two machines can interact with each other in the same way that you are kind of interacting with your devices when you are browsing the internet or using several applications.

Rules For Api Security Testing

Unfortunately, a lot of APIs are not tested to satisfy the security criteria, which indicates the API you are using may not be secure.

So, you have to assure that your applications are performing as expected with less risk potential for your data. You must test and assure that your API is safe.

Although, API testing is easy its implementation is hard. Here are some practices of API testing

  • An API should give expected output for a given input
  • The inputs should arrive within a specific range and values crossing the range must be denied
  • Any empty or null input must be denied when it is unacceptable
  • Wrongly sized input must be rejected

Methods Of API Security Testing

Fuzz Testing

It is one of the easy and common ways to test the delicacies in a web service.

It is essentially a black box software testing method that includes detecting bugs using malformed data injection.

Fuzz testing does not need advanced tools or programs. Fuzz testing can be done on any application whether it is an API or not.

You can easily use the command lines like curl and easily send some unexpected value to API and verify if it breaks. For example:

Fuzz Testing Numbers: If your API requires numbers in the input, try to assign values such as negative numbers, 0, and large digit numbers.

A badly coded application will depend on a specified format, so this is a good way to discover bugs in your application.

Fuzz Testing Strings: the best method of fuzz testing strings is to send SQL queries in a pattern where the API is expected some innocuous value.

Undoubtedly, an API will not operate any SQL sent is a request.

Command Injection

An injection flaw happens with respect to web services and API when the web application pass data from HTTP request through different commands such as system call, database command, or request to an external service.

For example, you send a request to an API by entering a command  ?command=rm -rf / inside one of the query parameters.

If the API does not verify the data within that parameter properly, then it could work that command by erasing the contents of the server.

Here we will consider the methods to test API vulnerabilities.

Operating System Commands in API Requests: You can begin with discovering the operating system on which the API operates. Generally, it works on Linux and Windows.

Now, try to send commands within the API request that would work on that operating system.

Consider the following case in which the API request deletes a file by name.

$fn = $_GET[‘filename’];

system(“rm $file”)

If the user’s request sends a vicious command in the filename parameter, then it will be executed like:;rm%20/

SQL in API parameters: As related to operating system command injection, SQL injection is a kind of instability that occurs when invalidating data from an API request is employed in a database command. For example

$name = $_GET[‘username’];

runDbTransaction(“UPDATE user SET username=$name WHERE id = …”)

An attacker or hacker can simply run a database command by building an API request if the input data is not verified properly.

(Un) Authorized Endpoints And Methods

It is very essential that an API should approve every single request before processing it because when the API exposes any sensitive data and enable the users to make damaging actions.

Test For Authentication On All EndPoints: This is one of the methods to test your API security is to set up automated tests in the situations such as test authorized endpoints without authorization, test authorized endpoints without authorization, and test user privileges.

Test Unhandled HTTP Methods: API that uses HTTP has several methods that are employed to retrieve, save and delete data.

The methods to set up a security test for these cases are utilizing HEAD to bypass authentication and test arbitrary HTTP methods.

Parameter Tampering

It takes the benefit of backend sanitizing errors and then handles parameters sent in API requests.

According to this, the forms that use type=” hidden” input should always be examined in order to ensure that the backend server accurately verifies them.

<input type=”hidden” name=”price” value=”100.00? />

Conceptually, when the user begins his web browser and changes the input value from 100.00 to 1.00, and presents the form, then the service will be vulnerable to parameter tampering.

API Security Testing Tools


It is a functional testing tool particularly designed for API testing. It enables the users to test is a functional testing tool particularly designed for API testing. It enables the users to test SOAP APIs, REST, and web services effortlessly.


  • It operates the test quickly and simply with point & clicks and drag & drop
  • The load tests and security scan employed in SoapUI can be reused for functional testing

Katalon Studio

It is a free security testing tool for API, web, and mobile applications. It maintains both REST and SOAP requests with several commands and functionality. It has the ability to combine UI and API for multiple environments.


  • It supports the data-driven approach
  • IT support CI/CD integration
  • It supports both SOAP and REST


It is a security testing tool employed to test web services and API. It was intended to send HTTP requests in an easy and quick way. Now it extends its solutions with the original version for both Mac and Windows.


  • It can be operated on Linux, Windows, Mac, and Chrome apps
  • It is simple to use a REST client
  • Rich interface
  • Practiced for automated and exploratory testing
  • It doesn’t need to learn a new language
  • It also has run, test, document, and monitoring features

Tricentis Tosca

It is a continuous security testing platform with various benefits and features


  • It maintains an array of protocols such as SOAP, IBM MQ, Rabbit MQ, JMS, etc.
  • API tests can be utilized across packaged apps, cross-browser, mobile, etc.
  • It decreases the time of regression testing


It is a cross-cloud API security testing tool that enables the users to test and measure the performance of API.


  • Powered by Javascript.
  • It enables design, monitor, scale, and deploys API.
  • Recognize performance issues.
  • Generate API proxies.

Also Read: Key Benefits Of API Testing For Your Business


The foremost essential thing is to follow the API security methods mentioned above. As they can give a sufficient layer of security to the API endpoint.

An average user may discover it cumbersome to discover and patch the vulnerability. In such an event, you can always go for automated security solutions such as TestUnity to test and defend your API.

At TestUnity, we strive for the highest quality in every project, and our professional QA specialists are ready to ensure it. Contact us if you’re looking for a dedicated team to enhance your product’s quality.


Testunity is a SaaS-based technology platform driven by a vast community of testers & QAs spread around the world, powered by technology & testing experts to create the dedicated testing hub. Which is capable of providing almost all kind of testing services for almost all the platforms exists in software word.

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