Insecure Direct Object Reference (IDOR) Vulnerabilities: Understanding, Exploiting, and Detecting

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Insecure Direct Object Reference, or IDOR, is a common security vulnerability that exposes sensitive data and allows unauthorized access to resources. It is a critical issue that often appears in the OWASP Top Ten, a list of the most prevalent security risks in web applications. In this blog post, we will discuss what IDOR vulnerabilities are, how attackers can exploit them, their position in the OWASP Top Ten, and how penetration testing can help detect these vulnerabilities.

Understanding IDOR Vulnerabilities

An IDOR vulnerability occurs when an application exposes direct references to internal objects, such as files, database records, or primary keys, without proper access control mechanisms in place. As a result, attackers can manipulate these references to gain unauthorized access to sensitive information or perform actions they should not be allowed to perform.

For example, consider a web application that uses numeric identifiers in the URL to represent individual user accounts:

In this case, an attacker could simply change the id parameter in the URL to access other users’ accounts:

Exploiting IDOR Vulnerabilities

Attackers exploit IDOR vulnerabilities by manipulating object references to access unauthorized resources. Some common techniques include:

  1. Enumeration: Attackers can increment or decrement object identifiers in URLs, API calls, or form fields to discover other objects they should not have access to.
  2. Guessing: Attackers can attempt to guess object references, particularly when the identifiers are predictable, sequential, or use easily guessed naming conventions.
  3. Scraping: Attackers may gather information from public sources, such as search engines, social media, or other websites, to find exposed object references.


Insecure Direct Object Reference vulnerabilities fall under the category “Broken Access Control” in the OWASP Top Ten. Broken Access Control vulnerabilities are ranked as the fifth most critical web application security risk in the 2021 edition of the OWASP Top Ten.

Detecting IDOR Vulnerabilities with Penetration Testing

Penetration testing, also known as ethical hacking, is an effective method for detecting IDOR vulnerabilities. It involves simulating real-world attacks to identify potential security flaws in an application. Here are some penetration testing techniques that can help identify IDOR vulnerabilities:

  1. Manual Testing: Penetration testers can manually explore the application to identify patterns in object references and attempt to manipulate them to access unauthorized resources.
  2. Automated Scanning: Testers can use automated scanning tools to discover potential IDOR vulnerabilities by sending various requests to the application and analyzing the responses.
  3. Code Review: A thorough code review can help identify insecure direct object references and inadequate access control mechanisms in the application’s source code.

IDORs are one of the most prevalent vulnerabilities found by Brackish Security testers during web or mobile application testing.


Insecure Direct Object Reference vulnerabilities pose a significant risk to web applications, allowing attackers to access sensitive information and perform unauthorized actions. Organizations should prioritize addressing these vulnerabilities by implementing robust access control mechanisms and conducting regular penetration testing to identify and fix potential security flaws. By doing so, they can ensure the confidentiality, integrity, and availability of their data and resources.