Navigating API Security - The OWASP API Security Top 10 2023

Navigating API Security - The OWASP API Security Top 10 2023

A guide on the OWASP API Security Top 10 2013. Understand the prevalent API vulnerabilities and discover effective strategies to secure your applications.

APIs (Application Programming Interfaces) are the backbone of modern web services and applications. APIs facilitate seamless interaction between different software components, allowing them to communicate effectively. However, as their use becomes more prevalent, so does their attractiveness to cyber attackers, making robust API security measures indispensable.

Adopting a security-first approach in your API development process is essential. This means incorporating security measures from the early stages of development and ensuring they are an integral part of your API development lifecycle.

OWASP (Open Web Application Security Project), a renowned non-profit organization dedicated to enhancing software security, has developed a set of guidelines known as the OWASP API Security Top 10 to help developers build secure APIs. This blog post aims to walk you through these guidelines and provide a comprehensive understanding of how to implement them effectively.

OWASP API Security Top 10 2023

The OWASP API Security Top 10 offers a list of the most common API vulnerabilities, providing developers with an understanding of the potential security risks associated with APIs. Here is candidate list of the updated top 10 API risks as per OWASP in 2023:

API 1:2023 – Broken Object Level Authorization (BOLA)

In this case, the API exposes endpoints that handle object identifiers, allowing unauthorized access. For example, an API may allow users to access their own profile using a URL like ``. If a user can simply change the "123" to "124" to view another user's profile, the API has Broken Object Level Authorization.

API 2:2023 – Broken Authentication

This occurs when an API allows attackers to impersonate other users or maintain their session. For instance, if an API uses predictable or insecure session IDs, an attacker might guess or brute-force these IDs to impersonate a user.

API 3:2023 – Broken Object Property Level Authorization (BOPLA)

The vulnerability of Broken Object Property Level Authorization (BOPA) transpires when an unauthorized individual manages to gain access to properties of an object that they should not be able to view or modify. This could happen through an exploitable authorization process flaw or a brute-force attack. A successful exploit can enable an attacker to illicitly procure sensitive data, manipulate existing data, or disrupt the API's regular operations.

API 4:2023 – Unrestricted Resource Consumption

The vulnerability of Unrestricted Resource Consumption manifests when an attacker successfully utilizes an excessive quantum of resources, such as processing power, memory, or bandwidth, from an API. This could occur by exploiting a security flaw in the API or employing a brute-force attack strategy. By consuming an excess amount of resources from an API, an attacker could disrupt its regular operation or, in extreme cases, lead to a complete shutdown of the API service.

API 5:2023 – Broken Function Level Authorization

APIs that don't correctly validate user roles and rights, allowing users to access privileged functions, suffer from this vulnerability. For example, a user with a 'reader' role could access an endpoint meant for 'admin' users, like

API 6:2023 - Unrestricted Access to Sensitive Business Flows

APIs susceptible to this risk reveal a business process, like purchasing a ticket or posting a comment, without accounting for potential harm to the business if the functionality is used excessively in an automated way. This issue isn't always due to implementation flaws.

API 7:2023 – Server-Side Request Forgery (SSRF)

Server-Side Request Forgery (SSRF) constitutes an attack in which an intruder deceives a victim into executing an unintended action. This could be achieved by dispatching a nasty link to the victim or embedding nefarious code in a website the victim frequents. An intruder successfully orchestrating a SSRF attack could enact a range of nasty actions. These may include unauthorized transfer of funds from a victim's account, making unauthorized purchases, or altering their account settings without their knowledge or consent.

API 8:2019 – Security Misconfigurations

This category includes vulnerabilities like verbose error messages, insecure default configurations, or unnecessary HTTP methods. For example, a misconfigured API might reveal sensitive information, like database details, in error messages.

API 9:2023 – Improper Inventory Management

Improper Inventory Management is a vulnerability when an organization inadequately manages its APIs. This lapse in oversight can precipitate various security risks, such as unauthorized access to sensitive data, data loss, and denial-of-service attacks.  An attacker who successfully exploits this vulnerability may acquire sensitive data, disrupt operations, or even cause the complete shutdown of an API.

API 10:2023 – Unsafe Consumption of APIs

Unsafe Consumption of APIs is a vulnerability that surfaces when an application or system does not correctly consume an API. This can instigate an array of security threats, such as unauthorized access to sensitive data, data loss, and denial-of-service attacks. An intruder who successfully exploits this vulnerability can potentially abscond with sensitive data, disrupt operations, or even cause a full-scale shutdown of an API.

While the OWASP API Top 10 provides a solid framework to understand the most common API security risks, it's also a nudge to remember that security isn't just about ticking off boxes. It's not merely a checklist to clear but a launching pad for a holistic approach to security. This approach includes being proactive, watching for potential issues, and continuously striving to improve. It underscores the intricate nature of API security and the need for an all-encompassing security strategy. It's a friendly reminder that in cybersecurity, there's always more to learn and improve upon!

Understanding these risks and how they can be exploited is the first step toward developing secure APIs. You can mitigate these risks by following the OWASP API Security best practices and adopting a proactive approach toward API security.

Mitigating OWASP API Security Vulnerabilities

Now that we've understood the top 10 API vulnerabilities let's discuss how developers can mitigate these vulnerabilities.

Object Level and Function Level Authorization: Ensure every API request undergoes stringent authorization checks. Implement checks for every function and data object a user can access.

User Authentication: Implement robust user authentication and session management mechanisms. Regularly review these mechanisms to ensure they are up-to-date and secure.

Data Exposure: Limit data exposure by only sending the data that are absolutely necessary for the user. Review your API responses and ensure no sensitive data is being exposed.

Rate Limiting: Implement proper rate limiting to protect your API from DoS attacks and ensure it isn't overwhelmed with requests.

Mass Assignment: Validate and filter the input received from the client. Use an allowlist for updating object properties.

Security Misconfiguration: Regularly review and update your API configurations. Ensure that error messages aren't providing sensitive information, unnecessary HTTP methods are disabled, and the default configurations are secure.

Injection Prevention: Adopt a strong validation process for all data received from clients, and use parameterized queries to prevent injection attacks. All data should be treated as untrusted, and any interpretation should be made cautiously.

Proper Inventory Management: Effectively managing APIs necessitates their proper identification, thorough documentation, systematic categorization, and clear assignment of ownership responsibilities. Make sure all API versions are documented and known. Remove non-production versions of the API and any older versions with security weaknesses. Regularly update your documentation to reflect the current state of your API.

Logging and Monitoring: Implement comprehensive logging and monitoring to ensure that any unusual activity or security incident is quickly identified and addressed. This should include detailed logs, suspicious activity alerts, and incident response procedures integration. 

Security Controls Implementation: Establish and implement suitable security controls for each API, tailored to its specific requirements and potential risks.

Developer Education: Educating developers about the nuances of API security can significantly reduce the risk of unsafe API consumption. Knowledge about potential risks and how to avoid them can lead to more secure coding practices.

Let's think of an API as a postman in a town.

The API (the postman) is responsible for delivering letters (data) from people (users) to different places (servers). The OWASP API Security Top 10 is like a set of guidelines the postman should follow to ensure the letters are delivered safely and correctly.

For example, one rule might be "Deliver the letters only to the correct address." This is similar to the "Broken Object Level Authorization" rule. If the postman delivers the letter to the wrong house, someone else might read your private letters.

Another rule could be "Do not share any details from the letters." This is like the "Excessive Data Exposure" rule. The postman shouldn't tell others what's written in the letters he delivers.

A rule like "Don't take more letters than you can handle" is similar to "Lack of Resources & Rate Limiting." If the postman tries to carry too many letters at a time, he might lose some or get too tired to do his job correctly.

So, the OWASP API Security Top 10 is like a list of essential rules that help the API (postman) deliver letters (data) correctly and securely, making sure the system (the town) runs smoothly.


The OWASP API Top 10 is a product of global teamwork! It's not just the brainchild of one person or a single organization but the collective wisdom of security professionals worldwide. This collaborative spirit makes the list comprehensive.

Another point that I find fascinating is that the OWASP API Top 10 isn't a static document - it's constantly evolving. As new threats and vulnerabilities pop up, the list adapts to stay relevant and reflect the shifting landscape of API security. This serves as a reminder that cybersecurity isn't a one-and-done deal; it's a dynamic field that requires constant vigilance and adaptation.

API security is a continuous journey rather than a one-time effort. Regular audits, penetration testing, and education for developers about the latest security threats and best practices are crucial for maintaining a secure API environment. Understanding and effectively implementing the OWASP API Security Top 10 guidelines is a significant step towards this goal. 

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