What is Broken Access Control? Broken Access Control is one of the most dangerous security risks in web applications, as highlighted in the OWASP Top 10. It occurs when applications fail to properly enforce authorization rules, allowing attackers to access, modify, or delete data they shouldn’t have permission to interact with. This flaw can lead to data breaches, account takeovers, and unauthorized administrative actions. How Does Broken Access Control Work? Access control determines what actions a user can perform within an application. If security controls are weak or misconfigured, attackers can: Common Examples of Broken Access Control 1. Insecure Direct Object References (IDOR) Scenario: Attackers modify a URL parameter to access other users’ data. 2. Forced Browsing Scenario: Unauthorized users access restricted pages by entering direct URLs. 3. Privilege Escalation Scenario: Attackers exploit permission misconfigurations to gain admin access. 4. CORS Misconfigurations Scenario: Misconfigured Cross-Origin Resource Sharing (CORS) allows malicious websites to access restricted data. 5. Weak API Access Controls Scenario: APIs expose endpoints without proper authentication or authorization checks. Broken Access Control Prevention Checklist ✅ Deny Access by Default: Ensure that all access is restricted unless explicitly granted. ✅ Implement Role-Based Access Control (RBAC): Assign users only the permissions necessary for their role. ✅ Use Secure Authorization Mechanisms: ✅ Restrict Direct Object References (IDOR Prevention): ✅ Secure API Endpoints: ✅ Enforce Session Management Best Practices: ✅ Use Proper CORS Configuration: ✅ Regularly Audit Access Controls: ✅ Monitor and Log Unauthorized Access Attempts: Final Thoughts Broken Access Control is a significant web security risk that can lead to severe data breaches and system compromise. By following best practices, implementing strict access control measures, and continuously monitoring security logs, organizations can effectively prevent unauthorized access and protect sensitive information. Broken Access Control Payloads with Examples Broken Access Control vulnerabilities occur when applications fail to enforce proper authorization, allowing attackers to manipulate requests and gain unauthorized access. Below are some common payloads and examples demonstrating how attackers exploit these flaws. 1. Insecure Direct Object References (IDOR) Payload Scenario: A website uses numerical user IDs in URLs, allowing attackers to access other users’ data by modifying parameters. Example: Vulnerable Request (Attacker’s Action) Exploitation: The attacker modifies the id parameter to access another user’s data. ✅ Fix: Implement user authentication checks on the server-side and use non-sequential identifiers (e.g., UUIDs). 2. Forced Browsing Payload Scenario: An attacker manually enters a restricted URL to access sensitive admin pages. Example: Attacker’s Request (Trying to access an admin panel without authentication) 🚨 Impact: If access controls are missing, the attacker gains unauthorized admin access. ✅ Fix: Implement role-based access control (RBAC) and check user permissions before serving admin pages. 3. Privilege Escalation via Parameter Tampering Scenario: A web application allows users to change their role by modifying hidden form fields. Example: Vulnerable Form Submission Exploitation: The attacker modifies the request using a tool like Burp Suite or Postman: 🚨 Impact: The attacker escalates their privileges from user to admin. ✅ Fix: Always enforce role validation server-side instead of relying on client-side controls. 4. API Authorization Bypass Payload Scenario: An attacker sends an unauthorized API request to delete another user’s data. Example: Vulnerable API Request 🚨 Impact: If the API does not validate user permissions, the attacker can delete another user’s account. ✅ Fix: Implement strict API authentication and authorization checks before processing requests. 5. CORS Misconfiguration Exploit Payload Scenario: A website allows all origins (*), enabling attackers to steal data via cross-site scripting. Example: Vulnerable CORS Configuration (Server Response) Exploitation: An attacker hosts a malicious website and tricks a logged-in user into running the following JavaScript: 🚨 Impact: The attacker steals sensitive user data using a Cross-Origin Request. ✅ Fix: Restrict CORS policies to trusted domains only and avoid Access-Control-Allow-Origin: *. Conclusion Broken Access Control is a serious vulnerability that attackers exploit to gain unauthorized access, escalate privileges, and manipulate sensitive data. To prevent these attacks:✅ Implement server-side access control checks✅ Use role-based access control (RBAC)✅ Avoid exposing sensitive identifiers in URLs✅ Enforce authentication and authorization on APIs✅ Regularly audit access controls and logs Advanced Broken Access Control Payloads with Exploitation Examples Broken Access Control vulnerabilities allow attackers to bypass authentication, manipulate permissions, and access unauthorized data or functions. Below are additional payloads and examples of real-world attacks that exploit these vulnerabilities. 6. Session Fixation Attack Payload Scenario: An attacker forces a victim to use a predefined session ID, allowing the attacker to hijack the session after login. Example: Attacker’s Predefined Session The attacker sends a phishing email with the following link: 🚨 Impact: If the server accepts the attacker-controlled session ID, the victim logs in, and the attacker can hijack their session. ✅ Fix: 7. HTTP Parameter Pollution (HPP) Payload Scenario: Some applications process duplicate parameters incorrectly, allowing attackers to override access controls. Example: Vulnerable Request Exploitation: If the application processes only the last parameter, the attacker gets admin privileges. ✅ Fix: 8. Bypassing Method-Based Access Control Scenario: Some applications allow restricted functions via GET but do not restrict them when using POST or PUT. Example: Blocked Request (GET) Exploited Request (POST Bypass) 🚨 Impact: If the application does not properly restrict methods, attackers can perform actions they shouldn’t. ✅ Fix: Enforce access controls across all HTTP methods, not just GET. 9. Tampering JSON Web Tokens (JWT) for Privilege Escalation Scenario: The application uses JWTs for authentication, but the signature is not properly verified. Example: Original JWT (Base64-encoded header and payload) Exploitation: The attacker changes the payload to: And removes the signature verification using: 🚨 Impact: If the server does not properly validate JWT signatures, attackers can escalate privileges. ✅ Fix: 10. Exploiting Insecure File Upload for Remote Code Execution Scenario: An application allows file uploads but does not validate the file type properly, enabling attackers to upload executable files. Example: Malicious File Upload (PHP Webshell) The attacker uploads a file named shell.php: Then accesses it via: 🚨 Impact: The attacker gains remote access to execute commands on the server. ✅ Fix: 11. Bypassing Two-Factor