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The Ultimate Guide to API Security in 2024!

January 2, 2024
Written by
Aneesh Bhargav

API attacks rose 400% in the first quarter of 2023. But that's just the tip of the iceberg. API abuse attacks are projected to double next year. The surge in API attacks isn't a mere statistic; it's a red flag waving in the face of complacency. 

In the face of these escalating threats, securing your APIs is not just a priority—it's a necessity. As we step into 2024, the landscape of API security is undergoing rapid transformations because of escalating cyber threats and continuous technological innovation. So ask yourself this: How well-protected are your APIs? Do you have what it takes to ensure the resilience of your digital infrastructure? 

This guide breaks down the latest OWASP API Security Top 10, its risks and smart strategies keep your digital infrastructure secured. Whether you're a developer, security architect, or simply a tech enthusiast, understanding these key concerns is important to make sure that you're protecting not only your organization but also the end users.

Table of Contents

OWASP API Security Top 10

  1. API 01:2023 Broken object level authorization
  2. API 02:2023 Broken authentication
  3. API 03:2023 Broken Object Property Level Authorisation
  4. API 04:2023 Unrestricted resources consumption
  5. API 05:2023 Broken function level authorization
  6. API 06:2023 Unrestricted access to sensitive business flows
  7. API 07:2023 Server side request forgery
  8. API 08:2023 Security misconfiguration
  9. API 09:2023 Improper inventory management
  10. API 10:2023 Unsafe consumption of APIs

OWASP API Security Top 10

The OWASP API Security Top 10 is a list of the most critical API security risks that organizations should address. The list is updated regularly to reflect the latest trends and threats. The 2023 edition of the list includes the following vulnerabilities:

API1:2023 Broken Object Level Authorization

Broken Object Level Authorization is a type of vulnerability that occurs when an API fails to properly validate and enforce access control rules at the object level. This means that an attacker can access unauthorized data or perform unauthorized actions on objects.

BOLA vulnerabilities usually occur when APIs rely on user-supplied input to determine which objects to access. For example, an API might allow a user to specify the ID of a user account in an API request. If the API fails to validate the user account ID, an attacker can take advantage of this and modify the ID to access the account of another user.

API2:2023 Broken Authentication

Broken authentication occurs when an API's authentication mechanism is weak or improperly implemented, allowing attackers to gain unauthorized access to the API and the data it protects. Broken authentication vulnerabilities can occur due to several factors, including:

  1. Weak passwords. If an API allows users to choose weak passwords, such as passwords that are short or easy to guess, attackers can easily brute-force their way into user accounts.
  2. Lack of multi-factor authentication. Multi-factor authentication adds an extra layer of security to user accounts by requiring users to provide additional proof of identity, such as a code from their phone.
  3. Improper session management. Attackers can hijack active sessions and obtain unauthorized access to user accounts if an API does not correctly manage user sessions.
  4. Failure to protect authentication credentials. Attackers can obtain authentication credentials from an API and use them to access it if the credentials are stored in an insecure way, such as being sent over an unencrypted channel or kept in plain text.

API3:2023 Broken Object Property Level Authorization

This type of API vulnerability happens when an API doesn't have the capability to properly enforce granular access control rules at the property level of objects. When this happens, an attacker could access or modify unauthorized properties of objects that can lead to potential data exposure, unauthorized actions, or privilege escalation.

BOLA vulnerabilities generally emerge when APIs expose objects with multiple properties and rely exclusively on object-level authorization checks. An attacker can exploit this weakness by crafting API requests that target specific properties of an object, even if they are not authorized to access the entire object.

API4:2023 Unrestricted Resource Consumption

Denial-of-service (DoS) attacks, as well as resource exhaustion and increased costs, can occur when an API fails to limit the amount of resources that users can consume. Unrestricted Resource Consumption vulnerabilities can occur due to a number of factors, including:

  1. Lack of resource limits. If an API does not enforce any limits on the amount of resources that users can consume, an attacker can send a large number of requests to the API that can cause it to become unavailable to other users.
  2. Inefficient API code. If an API code is inefficient, it can consume a large amount of resources even when handling legitimate requests. This can make it easier for an attacker to exhaust the API's resources with a relatively small number of requests.
  3. Lack of monitoring. An API that is not properly monitored can be difficult to detect and respond to URC attacks.

API5:2023 Broken Function Level Authorization

Broken Function Level Authorization is when an API fails to properly validate and enforce access control rules at the function level. This will provide a way for an attacker to execute unauthorized functions or access unauthorized data.

BFLA vulnerabilities typically occur when APIs rely on user-supplied input to determine which functions to execute or which data to access. For example, an API might allow a user to specify the name of a function in an API request. If the API fails to validate the function name, an attacker could modify the function name to execute an unauthorized function.

API6:2023 Unrestricted Access to Sensitive Business Flows

When an API exposes a sensitive business flow without compensating for how the functionality could harm the business if used excessively in an automated manner, it's when the Unrestricted Access to Sensitive Business Flows vulnerability can occur. When this happens, an attacker could exploit the API to disrupt business processes, harm the company's reputation, or even cause financial losses.

APIs that are designed without proper consideration of the potential consequences of automating business flows are the common reason why Unrestricted Access to Sensitive Business Flows vulnerability happens. For example, an API might allow users to purchase products without any limits on the quantity or frequency of purchases. An attacker could exploit this vulnerability to buy up all of the stock of a product, causing the company to lose revenue.

API7:2023 Server Side Request Forgery

Server Side Request Forgery (SSRF) is a type of attack that allows an attacker to force a server-side application to make an unauthorized request to an arbitrary external destination. Malicious actors use this to bypass security restrictions, access sensitive data, or even launch denial-of-service (DoS) attacks. 

SSRF vulnerabilities typically occur when an API accepts user-supplied input that is used to construct the URL of an external request. If the API does not properly validate this input, an attacker can inject malicious URLs that point to internal resources or external resources that they control.

API8:2023 Security Misconfiguration

Security misconfiguration is a broad term that refers to any error or oversight in the setup or configuration of a system or application that makes it vulnerable to attack. In the context of API security, security misconfiguration can occur at any level of the API stack, from the network level to the application level. Several factors can contribute to security misconfiguration in APIs, including:


  • A lack of clear and comprehensive security policies and procedures can lead to inconsistencies and oversights in configuring API security settings.
  • Manually configuring and managing API security settings can be error-prone and time-consuming. Automation can help to reduce the risk of human error and ensure that security settings are consistently applied across all environments.
  • Failure to promptly install security patches for operating systems, middleware, and API frameworks can leave APIs vulnerable to known exploits.
  • Many software components and applications come with insecure default configurations that need to be explicitly disabled or modified to enhance security.

API9:2023 Improper Inventory Management

Improper inventory management refers to the failure to properly identify, track, and maintain an up-to-date inventory of all APIs within an organization. This lack of visibility can lead to several security risks, including the existence of unidentified and unmanaged APIs, untracked API dependencies, outdated API versions, and unused or abandoned APIs. Issues like these can expand the attack surface, delay vulnerability discovery, hinder patching efforts, and lead to compliance violations.

API10:2023 Unsafe Consumption of APIs

Unsafe consumption of APIs is a common vulnerability that occurs when organizations fail to properly validate and sanitize user input, enforce granular access control rules, or implement adequate security measures when interacting with external or third-party APIs. This can lead to a range of security vulnerabilities, including Broken Object Level Authorization (BOLA), Broken Authentication, Unrestricted Resource Consumption (URC), Broken Function Level Authorization (BFLA), Unrestricted Access to Sensitive Business Flows (UASBF), Server-Side Request Forgery (SSRF), Security Misconfiguration, and Improper Inventory Management. Basically, the other API security vulnerabilities in this guide.

API Security with AppSecEngineer

Keeping your assets secure is an ongoing job. New challenges might pop up, but by staying alert, following good practices, and making sure everyone in your team is on board with safety, you're setting sail on a smoother, safer journey.

AppSecEngineer doesn't just offer courses; it's your go-to resource for understanding the ins and outs of API security. Our Playgrounds will help hone your best secure coding skills, put your new skills to the test with Challenges, and stop security breaches before they actually happen with Hands-on Labs

By staying informed and continuously honing your skills, you're not only safeguarding your organization but actively contributing to the collective resilience of the online world. 

Never stop learning with AppSecEngineer!

Source for article
Aneesh Bhargav

Aneesh Bhargav

Aneesh Bhargav is the Head of Content Strategy at AppSecEngineer. He has experience in creating long-form written content, copywriting, producing Youtube videos and promotional content. Aneesh has experience working in Application Security industry both as a writer and a marketer, and has hosted booths at globally recognized conferences like Black Hat. He has also assisted the lead trainer at a sold-out DevSecOps training at Black Hat. An avid reader and learner, Aneesh spends much of his time learning not just about the security industry, but the global economy, which directly informs his content strategy at AppSecEngineer. When he's not creating AppSec-related content, he's probably playing video games.

Aneesh Bhargav


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