Introduction to OWASP API Security Top 10 2023

Introduction to API

An Application Programming Interface (API) is a component that enables communication between two different systems by following certain rules. It also adds a layer of abstraction between the two systems where the requester does not know how the other system has derived the result and responded back.

Over the past few years, developers have started relying more on APIs as it helps them to meet the needs of today’s rapid application deployment model.

As the APIs started getting a wider acceptance it is highly critical to safeguard them by thoroughly testing their behavior and following best security practices.

Overview of OWASP API Security

The OWASP API Security project aims to help the organizations by providing a guide with a list of the latest top 10 most critical API vulnerabilities and steps to mitigate them.

As part of updating the old OWASP API Security risk categories of 2019, recently OWASP API Security Top 10 2023 is released.


What’s new in OWASP API Sec 2023?


List of vulnerabilities:

API1:2023 Broken Object Level Authorization

Broken Object Level Authorization (BOLA) is a vulnerability that occurs when there is a failure in validation of user’s permissions to perform a specific task over an object which may eventually lead to leakage, updation or destruction of data.

To prevent this vulnerability, proper authorization mechanism should be followed, proper checks should be made to validate user’s action on a certain record and security tests should be performed before deploying any production grade changes.

API2:2023 Broken Authentication

Broken Authentication is a critical vulnerability that occurs when application’s authentication endpoints fail to detect attackers impersonating someone else’s identity and allow partial or full control over the account.

To prevent this vulnerability, observability and understanding of all possible authentication API endpoints is needed, re-authentication should be performed for any confidential changes, multi-factor authentication, captcha-challenge and effective security solutions should be applied to detect & mitigate credential stuffing, dictionary and brute force type of attacks.

API3:2023 Broken Object Property Level Authorization

Broken Object Property Level Authorization is one of the new risk categories of OWASP API Security Top 10 2023 RC. This vulnerability occurs when a user is allowed to access an object’s property without validating his access permissions.

Excessive Data Exposure and Mass Assignment which were a part of OWASP APISec 2019 are now part of this new vulnerability.

To prevent this vulnerability, access privileges of users requesting for a specific object's property should be scrutinized before exposure by the API endpoints. Use of generic methods & automatically binding client inputs to internal objects or code variables should be avoided and schema-based validation should be enforced.

API4:2023 Unrestricted Resource Consumption

Unrestricted Resource Consumption vulnerability occurs when the system’s resources are being unnecessarily consumed which could eventually lead to degradation of services and performance latency issues. Although the name has changed, the vulnerability is still the same as that of Lack of Resources & Rate Limiting.

To prevent this vulnerability, rate-limiting, maximum size for input payload/parameters and server-side validations of requests should be enforced.

API5:2023 Broken Function Level Authorization

Broken Function Level Authorization occurs when vulnerable API endpoints allow normal users to perform administrative actions or user from one group is allowed to access a function specific to users of another group.

To prevent this vulnerability, access control policies and administrative authorization checks based on user’s group/roles should be implemented.

API6:2023 Unrestricted Access to Sensitive Business Flows

Unrestricted Access to Sensitive Business Flows is also a new addition to the list of API vulnerabilities. While writing API endpoints it is extremely critical for the developers to have a clear understanding of the business flows getting exposed by it. To avoid exposing any sensitive business flow and limit its excessive usage which if not considered, might eventually lead to exploitation by the attackers and cause some serious harm to the business. This also includes securing and limiting access to B2B APIs that are consumed directly and often integrated with minimal protection mechanism.

By keeping automation to work, now-a-days attackers can bypass traditional protection mechanisms. APIs inefficiency in detecting automated bot attacks not only causes business loss but also it can adversely impact the services for real users as well.

To overcome this vulnerability, enterprises need to have a platform to identify whether the request is from a real user or an automated tool by analyzing and tracking patterns of usage. Device fingerprinting, Integrating Captcha solution, blocking Tor requests, are a few methods which can help to minimize the impact of such automated attacks.

For more details on automated threats, you can visit OWASP Automated Threats to Web Applications

Note: Although the vulnerability is new but it contains some references of API10:2019 Insufficient Logging & Monitoring

API7:2023 Server-Side Request Forgery

After finding a place in OWASP Top 10 web application vulnerabilities of 2021, SSRF has now been included in OWASP API Security Top 10 2023 RC list as well, showing the severity of this vulnerability.

Server-Side Request Forgery (SSRF) vulnerability occurs when an API fetches an internal server resource without validating the URL from the user. Attackers exploit this vulnerability by manipulating the URL, which in turn helps them to retrieve sensitive data from the internal servers.

To overcome this vulnerability, Input data validations should be implemented to ensure that the client supplied input data obeys the expected format. Allow lists should be maintained so that only trusted requests/calls will be processed, and HTTP redirections should be disabled.

API8:2023 Security Misconfiguration

Security Misconfiguration is a vulnerability that may arise when security best practices are overlooked. Unwanted exposure of debug logs, unnecessary enabled HTTP Verbs, unapplied latest security patches, missing repeatable security hardening process, improper implementation of CORS policy etc. are a few examples of security misconfiguration.

To prevent this vulnerability, systems and entire API stack should be maintained up to date without missing any security patches. Continuous security hardening and configurations tracking process should be carried out. Make sure all API communications take place over a secure channel (TLS) and all servers in HTTP server chain process incoming requests. Cross-Origin Resource Sharing (CORS) policy should be set up properly. Unnecessary HTTP verbs should be disabled.

API9:2023 Improper Inventory Management

Improper Inventory Management vulnerability occurs when organizations don’t have much clarity on their own APIs as well as third-party APIs that they use and lack proper documentation.

Unawareness with regards to current API version, environment, access control policies, data shared with the third-party etc. can lead to serious business repercussions.

Clear understanding and proper documentation are the key to overcome this vulnerability. All the details related to API hosts, API environment, Network access, API version, Integrated services, redirections, rate limiting, CORS policy should be documented correctly and maintained up to date. Documenting every minor detail is advisable and authorized access should be given to these documents. Exposed API versions should be secured along with the production version. A risk analysis is recommended whenever newer versions of APIs are available.

API10:2023 Unsafe Consumption of APIs

Unsafe Consumption of APIs is again a newly added vulnerability covering a portion of API8:2019 Injection vulnerability. This occurs when developers tend to apply very little or no sanitization on the data received from third-party APIs.

To overcome this, we should make sure that API interactions take place over an encrypted channel. API data evaluation and sanitization should be carried out before using the data further. Precautionary actions should be taken to avoid unnecessary redirections by using Allow lists.


How F5 XC can help?


F5 Distributed Cloud (F5 XC) has a wide range of solutions for deploying, managing and securing application deployments in different environments.

XC WAAP is a F5 SaaS offering. The 4 key components of WAAP are Web Application Firewall, API Security, Bot Defense, DDoS Mitigation. All these solutions are powered on top of the XC platform. In addition to WAAP, F5 XC has other solutions to offer such as Fraud and Abuse, AIP, CDN, MCN, DNS and so on.

API security in XC WAAP simplifies operations with automated discovery of API transactions using AI/ML Engine along with insights of performance. It also provides API protection features like Rate Limiting, PII safeguard along with comprehensive security monitoring GUI dashboard. API security provides feasibility to import the inventory file in the form of swagger which helps to know exactly what endpoints, methods and payloads are valid, and this tightens security against abuse.

F5 XC management console helps the customers to leverage the benefit of monitoring, managing, and maintaining their application’s traffic from a single place irrespective of its platform on which it is hosted, it could be multi-cloud, on prem or edge.



This is an initial article covering the overview of proposed most critical API vulnerabilities from OWASP API Security community for 2023.

More articles covering detailed insight of each vulnerability and their mitigation steps using F5 XC platform will follow this article in coming days.

Meanwhile, you can refer to overview article for OWASP API Security Top 10 2019 which contains link to detailed articles covering API vulnerabilities of 2019 and how F5 XC can help to mitigate them.


Related OWASP API Security article series:

Updated Jun 05, 2024
Version 9.0

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