OWASP API Security

Last Updated on June 13, 2023 by Arnav Sharma

APIs are becoming increasingly popular in the software development world, allowing applications to communicate with each other and exchange data. However, with the growing popularity, there also comes an increase in security risks that need to be addressed. The Open Web Application Security Project (OWASP) has identified the top 10 security risks associated with APIs to help developers and organizations understand and mitigate these risks. In this blog post, we will be discussing the OWASP API Top 10, what each of the risks entails, and how you can take steps to prevent them. If you’re a developer or work with APIs, this post is a must-read to ensure that your APIs are secure and protected from malicious attacks.


OWASP API Top 10 Security Risks Overview

The OWASP API Top 10 is a list of the most critical security risks that can impact an application programming interface (API) and its users. APIs have become an integral part of many modern applications, providing access to data and functionality to a wide range of users. However, with this increased usage comes an increase in potential security risks that can lead to data breaches, system failures, and other security incidents.

The OWASP API Top 10 provides a comprehensive overview of the most common security risks when it comes to APIs. These risks include:

1. Broken Object Level Authorization
2. Broken User Authentication
3. Excessive Data Exposure
4. Lack of Resources & Rate Limiting
5. Broken Function Level Authorization
6. Mass Assignment
7. Security Misconfiguration
8. Injection
9. Improper Assets Management
10. Insufficient Logging & Monitoring

Understanding these risks is essential for developers and security professionals who are responsible for securing APIs. By identifying and mitigating these risks, organizations can better protect their data and users from potential security incidents. This overview of the OWASP API Top 10 security risks provides a foundation for understanding these risks and developing effective security strategies to address them.

1. Broken Object Level Authorization

Broken Object Level Authorization is a security vulnerability that occurs when an API fails to properly enforce access controls. It happens when an attacker is able to manipulate the API request and gain unauthorized access to sensitive data or functionality, regardless of their role or privileges within the system. This type of vulnerability can lead to data leaks, unauthorized data modifications, and even complete system compromise.

The root cause of this vulnerability often lies in insufficient validation and enforcement of user input at the application layer. The API may be designed with access controls in place, but if they are not properly implemented or tested, attackers can find ways around them. One common example is using modified or tampered requests to bypass object-level permissions and gain access to restricted resources.

To prevent Broken Object Level Authorization vulnerabilities in APIs, developers should take a defense-in-depth approach that includes proper authentication mechanisms such as session management and token-based authentication. Additionally, implementing strong authorization policies at both the application level and through operational processes can help reduce the likelihood of these types of attacks occurring.

2. Broken User Authentication and Session Management

Broken authentication and session management is a critical security issue that can result in unauthorized access to sensitive data. Attackers can exploit vulnerabilities in the authentication mechanisms used by an application to gain access to user accounts or even administrative privileges. This can happen due to weak passwords, session IDs that are predictable or easily guessable, or vulnerabilities in the application’s code that allow attackers to bypass authentication checks.

To secure user sessions, it is important to implement strong authentication mechanisms. This includes using strong passwords and enforcing password policies, such as regular password changes and password complexity requirements. Multi-factor authentication (MFA) can also be implemented as an additional layer of security to prevent unauthorized access.

Session management is another important aspect of securing user sessions. Session IDs should be unique and difficult to guess, and they should expire after a set period of time or when a user logs out. Session data should also be stored securely and encrypted to prevent unauthorized access.

Implementing secure session management also involves preventing session hijacking and fixing vulnerabilities in the application’s code that can allow attackers to bypass authentication and gain access to user accounts or sensitive data.

Overall, securing user sessions is critical for protecting sensitive data and preventing unauthorized access to user accounts. By implementing strong authentication mechanisms and secure session management practices, businesses can mitigate the risks associated with broken authentication and session management vulnerabilities.

3. Excessive Data Exposure

One of the top security vulnerabilities on OWASP’s list is excessive data exposure. This occurs when an API returns more data than necessary or exposes sensitive information to unauthorized parties. It can happen due to poorly designed APIs or inadequate access controls.

Excessive data exposure can lead to a variety of consequences, such as identity theft, fraud, and reputational damage for organizations. For instance, if an API returns too much information about a user’s personal details during an authentication process, it could allow attackers to steal their identity and use their credentials for malicious purposes.

To prevent excessive data exposure, developers should ensure that APIs only return the minimum amount of necessary information and implement proper access controls. They should also regularly test their APIs for vulnerabilities using tools like penetration testing and vulnerability scanning to identify any potential weaknesses in the system.

4. Lack of Resources & Rate Limiting

This vulnerability arises when an API does not have sufficient resources to handle incoming requests or if it does not limit the rate at which requests are made. When this occurs, attackers can overwhelm the system with a high volume of requests, causing it to crash or become unavailable.

Lack of resources and rate limiting can also lead to other vulnerabilities such as denial-of-service (DoS) attacks, where an attacker sends a flood of requests to an API with the aim of making it unavailable for legitimate users. Additionally, attackers may use this vulnerability to brute-force authentication credentials by repeatedly submitting login attempts until they successfully gain access.

To mitigate this vulnerability, APIs should implement proper resource allocation and rate-limiting mechanisms. This ensures that there is enough capacity to handle incoming requests while preventing excessive traffic from overwhelming the system. Rate-limiting also helps prevent brute-force attacks by limiting the number of login attempts within a given time frame. Overall, implementing these measures is crucial in ensuring that APIs are secure and available for legitimate users.

5. Broken Function Level Authorization

Broken function level authorization is one of the most common vulnerabilities in APIs. This type of vulnerability occurs when an API does not properly control access to its functions or endpoints. As a result, attackers can access functions or endpoints that they should not be allowed to access, leading to unauthorized access to sensitive data or functionality.

To secure APIs’ function-level authorization, it is important to implement proper access controls that limit the access of users to only those functions or endpoints that they are authorized to access. This can be achieved by enforcing role-based access control (RBAC) or attribute-based access control (ABAC), where access to functions or endpoints is granted based on the user’s role or specific attributes.

It is also important to implement proper validation of user input to prevent attackers from bypassing access controls by manipulating input parameters. This can be achieved by implementing input validation checks that ensure that user input is valid and does not contain any malicious code or character sequences.

Another important measure to secure APIs’ function-level authorization is to implement proper logging and auditing mechanisms that allow for the detection and investigation of suspicious activity. This can be achieved by logging all API requests and responses, including the user’s identity, the function or endpoint accessed, and any input and output parameters.

By implementing these measures, organizations can significantly reduce the risk of broken function level authorization vulnerabilities in their APIs and ensure that only authorized users can access sensitive data or functionality.

6. Mass Assignment

Mass assignment is a security vulnerability that arises when an attacker can modify fields in a data model without proper authorization. In other words, it is the ability to assign values to several attributes of an object at once, which can lead to unexpected changes in the behavior of the application. This vulnerability occurs when developers use frameworks or libraries that allow them to perform mass assignments without sufficient validation and sanitization. It is crucial for developers to implement proper access controls and input validation techniques to mitigate this vulnerability.

The OWASP Top 10 API Security Vulnerabilities highlights mass assignment as one of the common vulnerabilities found in APIs. Attackers exploit this vulnerability by modifying data fields that they were not authorized to change, such as changing user roles or privileges. A classic example of mass assignment attack occurred on GitHub where a hacker exploited a flaw in their API that allowed anyone with valid credentials but no permission restrictions to add collaborators or even delete entire repositories from any organization account.

To prevent mass assignment attacks, developers should avoid using frameworks or libraries that enable bulk updates without proper authentication and authorization mechanisms. They should also adopt secure coding practices such as input validation and output encoding techniques like white-listing, blacklisting, and typecasting before accepting user inputs. Proper error handling techniques should also be implemented so that attackers cannot extract valuable information from error messages returned by the application during invalid requests.

7. Security Misconfiguration: How to Secure Configuration for APIs

Security misconfiguration is one of the most common vulnerabilities that attackers exploit. Security misconfiguration is a result of poor configuration management practices that lead to the misconfiguration of servers, databases, and other software components. When it comes to APIs, security misconfiguration can expose sensitive data, provide unauthorized access to APIs, and can result in the compromise of the entire system.

To secure configuration for APIs, you need to start with a comprehensive inventory of all your APIs. This includes identifying the APIs you have, their locations, the type of data they transmit, and the authentication methods in place. Once you have established an inventory, ensure that you have a process in place to manage changes to the APIs. This process should include testing changes in a staging environment before deploying them to a production environment.

Another key aspect of securing configuration for APIs is to ensure that you have a process to manage access. This includes granting access only to authorized users, managing access control lists (ACLs), and ensuring that all authentication and authorization mechanisms are up-to-date and secure.

Finally, to mitigate the risks of security misconfiguration, you should regularly conduct vulnerability scans and penetration testing. This will help you to identify vulnerabilities in your API security configuration and take corrective action before the attackers can exploit them.

8. Injection Attacks

Injection attacks are one of the most common security risks that APIs face today. An injection attack occurs when an attacker uses malicious code or data to manipulate the behavior of an application, resulting in unauthorized access to sensitive data or functionality. Injection attacks can take many forms, including SQL injection, NoSQL injection, and LDAP injection, among others.

To mitigate and prevent injection attacks, it is important to implement strict input validation and output encoding controls. This means that all user inputs should be validated and sanitized to ensure that they do not contain any malicious code or data. Input validation should be performed at the server-side, and should include checks for data type, length, format, and range.

In addition, all output from the API should be encoded to prevent injection attacks. This includes encoding data that is displayed in HTML, JavaScript, or other user-facing interfaces. Encoding should be performed using secure coding techniques, such as HTML entity encoding or JavaScript object notation (JSON) encoding.

Finally, it is important to keep all software and system components up-to-date with the latest security patches and updates. This includes the operating system, web server, application server, and any third-party libraries or frameworks that are used. By following these best practices, you can reduce the risk of injection attacks and keep your API secure.

9. Improper Assets Management

Improper assets management is a significant concern in the context of API security vulnerabilities. APIs are designed to enable interoperability between different applications, but this can pose challenges when it comes to managing sensitive data and controlling access privileges. Improper assets management can refer to anything from incomplete or inaccurate asset inventories to poor access controls and weak authentication mechanisms.

One of the main risks associated with improper assets management is data leakage or theft. If an API is not properly secured, an attacker could potentially gain access to sensitive data such as user credentials, payment information, or confidential business records. In addition, inadequate asset tracking can make it difficult for organizations to detect unauthorized activity and respond effectively in the event of a security breach.

To mitigate the risk of improper assets management in APIs, organizations should prioritize implementing strong access controls and authentication mechanisms. This may include measures such as two-factor authentication, role-based access control, and encryption for sensitive data at rest and in transit. It’s also important for organizations to maintain up-to-date inventory lists that accurately reflect all assets related to their APIs so that they can monitor them closely for any signs of suspicious activity.

10. Insufficient Logging and Monitoring: How to Monitor and Detect API-related Events

Insufficient logging and monitoring is a significant security risk for APIs. It’s essential to have a robust logging and monitoring system in place to detect potential threats and attacks. When developing an API, it’s important to consider the types of events that should be monitored, such as authentication and authorization failures, data leaks, and any other suspicious activity.

An effective monitoring solution should be able to provide real-time and historical data about API-related events, including user activity and system performance. This includes logging all requests and responses, as well as monitoring the activities of third-party services and applications that interact with the API.
To ensure that the monitoring system is effective, it’s crucial to establish a baseline for normal API behavior. This baseline should include metrics such as response time, data transfer rates, and other key performance indicators. Deviations from this baseline can then be used as indicators of potential security threats or attacks.

It’s important to note that monitoring and logging is not just a one-time task, but an ongoing process. Regular reviews and analysis of the data collected can help identify potential security risks and improve the overall security posture of the API. With proper monitoring and logging in place, organizations can detect and respond to security incidents before they become significant threats.

Insufficient Attack Protection: How to Protect Against API Attacks

API attacks can be a nightmare for businesses, and the consequences can be costly, both financially and in terms of reputation. It’s important to take steps to protect against potential attacks.

One way to protect against API attacks is to implement strong API security measures, such as authentication and access controls, to ensure that only authorized users are able to access the API. This can help prevent unauthorized access to the API, which is a common attack vector for cybercriminals.

Another important step to take is to regularly monitor your API traffic for suspicious activity. This can help you detect and respond to potential attacks in real-time, before any significant damage is done.

Additionally, it’s important to keep your API up to date with the latest security patches and updates. This can help ensure that any known vulnerabilities are addressed and that your API is as secure as possible.

Finally, it’s important to have a plan in place to respond to a potential API attack. This includes having a dedicated incident response team, clear communication channels, and a plan for restoring service and mitigating any damage that may have been done.

By implementing these measures, businesses can help protect themselves against API attacks and ensure that their APIs remain secure and reliable.


Using Vulnerable Components: How to Keep API Dependencies Secure

APIs are only as secure as the components they use. Therefore, it’s important to keep all of your API’s dependencies secure. The first step in doing this is to know what dependencies your API uses and to monitor them for any changes or vulnerabilities that may arise.

One way to keep your dependencies secure is to regularly check for updates and patches that address security vulnerabilities. This can be done manually or through the use of automated tools that scan for vulnerabilities in your API’s dependencies.

Another way to keep your API dependencies secure is to use only trusted sources. This means avoiding the use of third-party components that have not been vetted by a reputable source. Additionally, you should only use dependencies from sources that you trust and that have a proven track record of providing secure components.

It’s also important to consider the impact of any new dependencies on your API’s overall security posture. For example, if you’re considering adding a new component to your API, you should evaluate its security implications before integrating it.

Finally, make sure to keep your API dependencies up-to-date. This means regularly checking for updates and patches and applying them as soon as possible. By staying on top of your dependencies, you can help to ensure the security of your API and the data it handles.


Conclusion and Next Steps

In conclusion, the OWASP API Top 10 is a valuable resource for understanding and mitigating key security risks in API development. By following the guidelines outlined in this list, you can help ensure the security of your APIs and protect your organization from potential attacks and data breaches.

It is important to note that security is an ongoing process and it requires continuous monitoring and improvement. It’s crucial to stay updated with the latest security threats, vulnerabilities, and mitigation techniques.

As a next step, you can start by conducting a thorough review of your API infrastructure to identify any potential vulnerabilities and risks. You can use the OWASP API Top 10 as a reference guide and implement the necessary security measures to address the identified risks.

Additionally, you can also consider engaging a third-party security expert to conduct a comprehensive security audit of your API infrastructure. This can help identify any potential vulnerabilities that may have been missed and provide recommendations for mitigating these risks.

Overall, securing your APIs is critical in today’s digital landscape and should be a top priority for any organization that utilizes APIs in their business operations. By following the OWASP API Top 10 and implementing the necessary security measures, you can help ensure the security and integrity of your API infrastructure.


Q: What is OWASP API Security Top 10?

A: OWASP API Security Top 10 is a list of the most critical API security risks, made by the Open Web Application Security Project (OWASP) to help organizations identify and mitigate security vulnerabilities in their APIs.

Q: What are some of the top API security risks?

A: Some of the top API security risks identified by OWASP include insufficient authentication/authorization, unprotected API endpoints, lack of encryption, and insecure data storage.

Q: Why is API security important?

A: API security is crucial for protecting sensitive data and preventing unauthorized access and attacks, which can lead to data breaches, financial losses, and damage to an organization’s reputation.

Q: What are some best practices for API security?

A: Some best practices for API security include implementing strong authentication and access controls, using encryption for data in transit and at rest, performing thorough input validation and error handling, monitoring for suspicious activity, and keeping APIs up-to-date with security patches and fixes.

Q: What is the difference between API security top 10 2023 and API security top 10 2019?

A: The API security top 10 list is updated periodically to reflect changes and updates in the API security landscape. The API security top 10 2023 will be the latest version of the list, while the API security top 10 2019 is a previous version.

Q: What is an API endpoint?

A: An API endpoint is a URL that represents an object or resource in an API. API endpoints are typically used to access and manipulate data in the API.

Q: What is an attack surface?

A: An attack surface is the sum total of all the possible vulnerabilities and security risks that an application or system may have that could be exploited by attackers.

Q: What are authentication tokens?

A: Authentication tokens are small pieces of data that are used to authenticate and verify the identity of a user or system accessing an API. Tokens are typically generated by an API when a user logs in or performs a specific action, and are used to authenticate subsequent API calls.

Q: What is a denial of service (DoS) attack?

A: A denial of service (DoS) attack is a type of attack that attempts to overwhelm a system or network with a flood of requests or traffic, rendering it inaccessible or unusable for legitimate users.

Q: How can organizations mitigate API security risks?

A: Organizations can mitigate API security risks by implementing best practices for API security, performing regular security assessments and testing, using security tools and solutions, and staying up-to-date with the latest security vulnerabilities and threats.


keywords: owasp api security project, top 10 api security risks, unique vulnerabilities and security risks, api vulnerability, api versions and exposed debug, deployed api versions, common api

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