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Most Common API Security Vulnerabilities

Published on Dec 14 2022

APIs are the cornerstone of modern business through the digital means and web app development due to their functionality, widespread adoption, and expanding architectural options. As with many technological advances, the benefit is accompanied by new risks and threats. 

APIs are frequently the target of cyberattacks such as distributed denial of service (DDoS). Understanding the most common API vulnerabilities is critical for developing an effective API security strategy. 

This article discusses API vulnerabilities, including the most common ones, and how to avoid them. 

What is API? 

API (Application Programming Interface) connects services and shares information. APIs mediate communication between a client application and a server-based or web-based services. They allow programs to talk to one another, share information, and respond to commands. 

Programmers use APIs to create a user-friendly interface for the end user, who may be a customer, an employee, or a business partner. 

In addition to bolstering security, APIs separate applications and server communication. Instead of allowing 3rd party apps to access the company’s servers, APIs form a medium between the server and 3rd party apps to handle requests. APIs can access servers securely without compromising the company’s data. 

What is API Vulnerability? 

The convenience APIs offer is not risk free, as APIs often have access to sensitive information and can be accessed over the internet like any other URI. This means that they share the vulnerabilities, are susceptible to attacks like any other online resource, and are frequently targeted by cybercriminals. 

What are the top API Vulnerabilities?  

Securing the API's vulnerabilities is daunting, so attention must be paid to the most prevalent vulnerabilities that cause severe adverse outcomes like breaches and stolen data. 

Here are the most common API vulnerabilities:  

1. Weak Authentication 

First and foremost, security hinges on authentication, which checks if the people or machines using it are who they claim to be. Without authentication, hackers can easily gain access to the system, hijack user accounts and sessions, steal sensitive information, and conduct fraudulent transactions. 

Sadly, this is the norm, as most companies either fail to take authentication seriously or employ inadequate safeguards, such as simple passwords and weak account lockout policies. 


  • Using strong passwords 
  • Using mandatory two-factor authentication  
  • Using authentication that does not rely on API keys 

2. Security Misconfiguration 

Due to the interaction between virtual machines, the cloud, and on-premises infrastructure, API ecosystems are notoriously difficult to comprehend. Because each API has its own specification and associated infrastructure, there is a high probability of security misconfigurations, such as missing security patches, unencrypted data in motion, overly detailed error messages, and unsecured cloud storage. 


  • Routine evaluation and auditing of API security settings 
  • Private or non-relevant technical information should be excluded in error messages 
  • DDoS attacks can be mitigated by imposing rate limits on request processing 

3. Excessive Data Exposure 

Excessive data exposure occurs when the client side of the application provides excessive data, which may result in severe penalties if legally protected-sensitive data is made public. Cybercriminals exploit these flaws by evading the client or monitoring traffic to detect overly detailed API responses. 

Such flaws can be disastrous; for example, excessive data exposure about an upcoming product may allow cybercriminals to spy on them, resulting in lost sales, reputational damage, or even IP theft. 


  • Only provide the minimum required information to fulfil the client's request 
  • Data filtering at the API level as opposed to the client level 
  • Monitoring and regulating scenarios for transmitting sensitive personal data 

4. Broken Object Level Authorization (BOLA) 

When an API uses only product IDs to determine which product the client has requested, this vulnerability is known as Broken Object Level Authorization (BOLA). It leaves certain sensitive fields within the object open to modification by the cybercriminal, who may proceed to change the IDs, delete them, or even take over the account. 


  • Complex and unpredictable IDs complicate setup 
  • Using a combination of identifiers and a check to see if the current user has permission to access the resource in question 


Attackers can trick the application programming interface (API) into performing malicious actions or gaining unauthorized access by inserting malicious data into the system via user input fields. Many different command lines can inject malicious commands, such as JavaScript, SQL, and NoSQL. 

To steal information, spy on the attacked system, or even take over the entire system is all within the realm of possibility with these types of attacks. 


  • Prevent using SQL or any other untrusted data types 
  • Accounts that make unusual requests should be temporarily disabled 
  • Use the programming libraries available for APIs to validate data and prevent invalid values 


While APIs can improve business development efficiency, they also increase the system's vulnerability. As a result, protecting APIs is critical, as is awareness of the most common threats. APIs are vulnerable to attacks that can compromise sensitive information, cause financial losses, or tarnish their reputation due to the vulnerabilities discussed in this article. 

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