Insecure Direct Object References (IDOR) is a security vulnerability that occurs when an application allows users to access or modify resources or data by manipulating input parameters, such as URLs or form fields, to reference objects that they are not authorized to access. This issue arises when an application exposes internal object references, such as file names, database records, or session identifiers, without proper access controls.

• Object References: Insecure Direct Object References typically involve the use of predictable or guessable object references in URLs or other request parameters. For example, if an application allows users to access files based on a file ID in the URL, an attacker may alter the ID to access other users' files.
• Lack of Access Controls: The vulnerability arises when the application does not adequately enforce access controls to ensure that users can only access objects they are authorized to view or modify. This can lead to unauthorized access or manipulation of sensitive data.
• Example: An example of IDOR could be a URL like `https://example.com/profile?userID=123`, where a user with ID `123` can access their profile. If an attacker changes the `userID` parameter to `124`, they may gain access to another user's profile if the application does not check the user's authorization.

• Access Control Validation: Implement strict access control mechanisms to verify that users have the appropriate permissions before granting access to resources or data. This should include checking user roles and ownership of objects.
• Avoid Predictable References: Avoid using predictable or sequential identifiers for sensitive resources. Instead, use random or obfuscated identifiers to reduce the risk of unauthorized access through manipulation.
• Parameter Validation: Ensure that input parameters used to access resources are validated and sanitized to prevent manipulation. Implement server-side checks to verify that the requesting user has the right to access the requested resource.

• Regular Security Testing: Perform regular security assessments, including penetration testing and code reviews, to identify and address potential IDOR vulnerabilities.
• Monitoring: Monitor logs and user activities for signs of unusual or unauthorized access patterns that may indicate an IDOR attack.

• https://owasp.org/www-community/attacks/Insecure_Direct_Object_References
• https://en.wikipedia.org/wiki/Insecure_Direct_Object_References
• https://www.acs.com.hk/en/products/283/acr1281u-c1/