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Securing APIs: Understanding and Exploiting Broken Authentication in API2:2023 


    Broken Authentication is a vulnerability that can Disclose web applications and APIs to unauthorized access. Testing and exploiting this vulnerability is crucial to identify and remediate potential security flaws. In this blog, we will explore how to test and exploit Broken Authentication using popular tools like Postman and Burp

    Suppose there is an e-commerce API called “ShopAPI” that allows users to browse and purchase products. The API implements a simple authentication mechanism using a username and password. However, due to a flawed implementation, it is susceptible to Broken Authentication.

    Step 1: Identify the Mechanism of Authentication:

    1. Make a request to an API endpoint that requires authentication using Postman.
    2. Check the authentication mechanism used, such as basic authentication, token-based authentication, or session-based authentication.

     The initial step is to learn how the target API handles authentication. This data will assist us in identifying potential vulnerabilities. We send a GET call to the API’s “products” endpoint without giving any authentication credentials using a tool like Postman. We receive a successful answer with a product list. This signals the possibility of a Broken Authentication vulnerability

    Step 2: Testing for Broken Authentication:

    Once we understand the authentication mechanism, we can proceed with testing for Broken Authentication vulnerabilities. To test for weak password policies, we create a new account by sending a POST request to the “register” endpoint with arbitrary credentials. The API accepts the weak password without enforcing any complexity requirements or length restrictions. This vulnerability allows us to create accounts with weak passwords that are easy to guess.

    1. Use Postman to send a request to the login endpoint with valid credentials.
    2. Capture the request using Burp Suite’s Intercept feature.

    Step 3: Analyzing the Authentication Process:

    In this step, we will analyze the intercepted request in Burp Suite to identify any potential vulnerabilities. Eventually, we discover a valid username and the corresponding weak password. By successfully logging in, we gain unauthorized access to the user’s account. With control over the account, we can perform malicious activities, such as modifying personal information, making unauthorized purchases, or accessing sensitive data associated with the account.

    1. Inspect the request headers and parameters related to authentication.
    2. Look for any issues such as weak password policies, lack of session management, or insecure transmission of authentication data.

    Step 4: Exploiting Broken Authentication:

    Once we have identified potential vulnerabilities, we can proceed with exploiting them to gain unauthorized access. With a weak password in hand, we attempt to gain unauthorized access to a user’s account. We use Postman to send a POST request to the “login” endpoint with the victim’s username and the weak password. Since the API does not implement any account lockout or rate limiting mechanisms, we can perform multiple logins attempts without raising suspicion.

    1. Use Burp Suite’s Repeater or Postman to replay the intercepted login request.
    2. Modify the request parameters to test for common vulnerabilities, such as weak passwords, SQL injection, or bypassing authentication mechanisms.
    3. Observe the server’s response to identify successful exploitation and gain unauthorized access.

    Step 5: Reporting and Remediation

    After exploiting the vulnerability, it is essential to report the findings to the relevant stakeholders and assist in remediation efforts.

    1. Document the procedures followed, including the vulnerabilities and impact discovered of the exploitation.
    2. Provide thorough mitigation recommendations, such as creating tighter password restrictions, enforcing session management best practices, and safeguarding authentication data transmission.


    API2:2023 Broken Authentication testing and exploiting is critical for identifying potential vulnerabilities and strengthening the security of online applications and APIs. Security professionals can uncover authentication method flaws and replicate real-world attacks using tools such as Postman and Burp Suite. To ensure the adoption of robust authentication mechanisms, it is critical to disclose results and assist in the remediation process


    API2:2023 Broken Authentication – OWASP API Security Top 10

    API2:2019 Broken User Authentication – OWASP API Security Top 10

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