API Security Testing: Checklist & Rules 

API stands for Application programming interface. Multiple applications can communicate with one another using API. It works by following a set rules. A breach of API security could lead to the disclosure of sensitive data by malicious actors. This article explains the why, how, and what of API security testing.

API can be described as a language that is used by many applications. You can easily add your Twitter handle to the sidebar of WordPress without having to code. This is because WordPress uses the Twitter API. Since the 1970s, APIs have been used by programmers and developers as well as their clients. What makes API security testing so important?

Every year, thousands of APIs are made available online. A recent study estimates that the global cloud API market will reach US$ 1,424 million by 2025. One of the main factors driving the rapid growth of the API market has been the rapid rise in cloud adoption. APIs have become the main language for enterprise integration. There are security risks associated with increasing API adoption.

Gartner, a research firm, predicts that API abuses will be the most prevalent type of attack on web applications by 2022. It is crucial to secure them for a smooth operation of a digital business. An API security assessment is the first step in achieving this.

What is API Security Testing?

API security refers to protecting API endpoints against attackers and creating secure APIs. An API that is vulnerable could result in:

  • Unauthorized Access
  • Data leakage
  • Sanctioning Fuzzy input
  • Injection Vulnerabilities
  • Parameter Tampering, etc.

Are you unsure if your website is violating API rules? Keep reading until the end. This blog contains all the API security testing methods you need to better protect your API. This is all in one minute.

Let’s first look at some of the API security flaws and the tools that can be used to identify them.

Security issuesTools for Testing
Injection Flaw
Burp Suite, Proxy, SQLmap, Astra Security Scan
Broken AuthenticationBurp Suite, Manual Testing, Astra Security Scan
Data ExposureAcunetix Security Scan, DirBuster, Astra Security Scan
XSSBurp Suite, Manual Testing, Astra Security Scan

API allows data to be exchanged between applications, as we have already stated. Hackers can gain access to sensitive data stored on your website if API security is breached.

Another possible outcome of an API security breach is:

  • Data leakage. These data are then sold via the dark web.
  • Your website and business may be defaced. It can have a severe impact on your reputation and brand’s standing in the marketplace.
  • Both revenue and number of users are on the decline.
  • If you are sued for negligence,

These API security breaches at popular companies will give you a better picture of the situation.

  • Airtel API was discovered to leak the information of customers by using only their numbers. Airtel has around 325 million users, according to estimates. The result could have been catastrophic, however.
  • A bug CVE-2018-5786 in the File Reader API was discovered in 2019. This vulnerability was found in all major browsers. It was exploited by hackers to attack Chrome users.
  • Hostinger, a well-known hosting provider, claimed that one of its servers had been hacked. The attackers were then able to access the internal API. The details of approximately 14 million clients were stolen
  • JustDial, India’s largest search engine platform, was accused of leaking the entire customer database of more than 100 million users. Leaked data included names, email addresses, mobile numbers, date, gender, occupation, and photos. It was basically all data that was provided by the company’s website, app, customer support system, and everything else, which was leaked.

We can help your company avoid similar situations. Continue reading.

Your API calls should be the most secure interaction on the Internet

Our API security checklist is detailed and carefully curated.

What is the REST API?

REST refers to an API design style. It stands for Representational state Transfer. It is the design style that API developers follow when creating an API.

Nearly all major companies, such as YouTube and Facebook, use REST API. REST API can be used internally or externally. REST API can be used in nearly all open-source CMSes, such as WordPress and Magento.

Remember that REST API is a designing style of an API and therefore is platform-independent. Rest API can be implemented using any language, such as PHP, Python, and others. Typically, data is exchanged using XML and JSON. It is not always specified.

Continue on.

The REST API has vulnerabilities. If you don’t want to be vulnerable, it is important to be aware of the most common vulnerabilities.

It’s time to uncover the truth and dispel some myths regarding API security.

1. API security is an integral part of API

API security is often viewed by consumers as a feature. It is not a feature. It is a different technology. Secure your API requires you to look beyond the API. API security is not a feature, but a mindset.

2. Software to secure your API can suffice

Software-based API security can be an option when you manage your API. It is quite convenient and may give you the impression that everything is fine. You’d be wrong and history will prove it. Software is the root cause of all the API security breaches. Running alien code on your website will leave you open to a host of vulnerabilities. You should consider API security testing as a concrete option.

3. It’s easy

API can be summarized as a concept with little effort: two programs are connected via an API. API security isn’t always so simple. This is why you might consider getting advice from an expert in the field. Ironically, the more complicated your API connection, the harder it will be to secure it. API security is a complicated task in today’s modern world. It involves sharing data and securing it.

4. API gateway is the exact same as API security gateway

As a solution for API security issues, API security gateways should be used constantly. Security gateways can limit data flow to the point that it is necessary and prevent you from losing data that does not need to be there. While a normal API gateway may be useful for your connection, it won’t compare to a secure one.

5. APIs automatically mean better security

Many companies claim that their products are safe because they use API security features. They believe API security is the best security. This is false. However, just because your product has API security features doesn’t make it more secure. An penetration test of APIs can help you find the vulnerabilities that could lead to hack.

Although APIs may increase your security and protect you, they won’t keep you protected enough by themselves.

Steps for API Security Testing

1. Check for API Input Fuzzing

Fuzzing is simply the act of providing random data to an API until it spills out something – some information, an error message or any other indication that random data was processed by the API.

You can use 0 or negative numbers, or very large numbers for numerical inputs. You can use SQL queries, system commands, or random characters to input string data to the API. Fuzzapi is an open-source fuzzing tool that automates the entire process.

These steps will help you use Fuzzapi

Step 1 – Download and Install Fuzzapi. This will show you how to do it.

Step 2 Now, after Fuzzapi has been installed, open your browser to navigate to localhost:3000. The image below will show you what it looks like.

Step 3 Enter the URL you wish to test in the URL box. Choose the method you prefer. You can add information to the Raw Headers or Parameters fields, if necessary. Otherwise, leave them empty. Click the Scanbutton.

Step 4 – Let the test continue. If the API is insecure, the final results will look like the image below.

2. Test for API Injection Attacks

a) SQL Injection (SQLi)

SQLi attacks work best when unsanitized API inputs are processed by the database. It is therefore important to test your REST API against SQLi bugs. You can use the following SQL commands as input:

'or 1=1--
"and 1=1--

These values may be used to bypass restrictions and return 200 OK if the API is susceptible to SQLi (error-based or SQLi). i.e.

www.xyz.com/api/auth-token/user=admin'or 1=1--

Although the API may be vulnerable to SQLi, but it is not always error-based or vulnerable, it could still produce a DBMS error in a message and respond with 500 Internal error. As shown in the image.

You can automate the process by using SQLmap.

b Command Injection

You can also inject API inputs using various OS commands. These commands are executed on the server. The commands for different Operating Systems (Windows, Linux, etc.) will be different. The command rm/”can delete the entire root directory on a Linux system. rm%20/ would be the URL encoded version of this command.

If an API is used to view the site’s contents, malicious code could be executed as follows:


The semicolon following the terminates the input parameter and executes an OS command. This command can cause the directory to be deleted. You might try something less dangerous like:


You can automate the process by using Commix.

3. You can test for parameter manipulation

Many parameters that are sent via an API request can be vulnerable to being tampered with. An attacker can alter the product’s values and make it almost free by tampering with them.

If, for example, there is a hidden field on the form that the user submitted like this:

An attacker can alter the value of the product from 100.00 to 1, almost for free. You can do this using any browser’s element inspector. Also, make sure you test hidden fields when sending requests to your API Endpoint.

4. Test for unhandled HTTP Methods

Many HTTP methods are used by web applications that communicate with API. These HTTP methods can be used to save, remove or get data. If a server doesn’t support an HTTP method, it will usually display an error message. This is not always true, especially with vulnerable APIs.

You can test for this vulnerability by sending a HEAD request from your API endpoint that requires authentication. There are many ways to send HEAD request. This can be done using Python. Simply add the following code into a python script, and run it.

import requests x = requests.head('API-URL') print(x.headers)

Replace API URL by the URL that you want to test.

  • Everything is fine if you receive a 405 or 501 method that is not allowed.
  • If you receive a 200 OK without authentication, it could be a vulnerability.

API Security Best Practices

  • Use access tokens. To maintain authorization, users can obtain access tokens by signing up. Every time a user requests an API, they must validate their Access tokens. You can also revoke or reset your token.
  • SSL is used to encrypt HTTP traffic to and from your API.
  • Always clean any input parameters that are sent to API. This should include the access token.
  • Limit the number requests to your API by any user per minute
  • To scan all API requests, use a security option.

Image: API Security Testing Infographic

In conclusion

It is important to adhere to the API security guidelines. They can add a layer of security to your API endpoint.

If your API is still compromised, Get immediate professional assistance .

It’s not uncommon to find it difficult to patch the vulnerability. To test and secure your API, you can always use automated security tools such as Astra.


1. What is the time frame for API Secuity testing

API security testing should take between 4 and 5 days. The vulnerabilities will be visible on your dashboard as soon as the second day passes. You may see a slight variation in the timeline depending on the scope of your test.

2. What is the cost of API security testing?

API testing costs between $349 to $1499 per scan, depending on how many scans you need and what the scope of your pentest.

3. Why choose Security Testing?

The best features: 1250+ tests, global security standards, intuitive dashboard that displays vulnerabilities and severity, simultaneous remediation assistance, security audit, multiple rescans. These are just a few of the many things that make Astra stand out from its competitors.

4. Are there rescans available after a vulnerability has been fixed?

You can get up to 2 rescans, depending on which plan you have. The rescans can be used within 30 days of the initial scan’s completion, even if a vulnerability has been fixed.