Insecure CORS Policy Template

Executive Summary:

This report addresses a critical security vulnerability regarding Insecure Cross-Origin Resource Sharing (CORS) Policy within our application. Insecure CORS Policy occurs when the Cross-Origin Resource Sharing policy is not properly configured, allowing unauthorized origins to access sensitive resources, leading to security risks such as data theft, session hijacking, or unauthorized API access. This report aims to detail the vulnerability, its potential impact, and recommendations for mitigation.

Description of the Vulnerability:

Insecure CORS Policy vulnerabilities arise when the Access-Control-Allow-Origin header is configured to allow requests from any origin (wildcard *) or from untrusted origins, without proper validation or restriction. Attackers can exploit these vulnerabilities to conduct cross-site request forgery (CSRF) attacks, steal sensitive data, or perform unauthorized actions on behalf of authenticated users by abusing the trust established through CORS policies.


The impact of Insecure CORS Policy vulnerabilities can be severe, leading to security risks such as unauthorized access to sensitive data, compromise of user sessions, or exploitation of API endpoints. Attackers can exploit these vulnerabilities to bypass same-origin policy restrictions, exfiltrate confidential information, or manipulate user interactions, potentially resulting in financial loss, reputational damage, or legal consequences for our organization.


The likelihood of exploitation depends on various factors, including the accessibility of sensitive resources with relaxed CORS policies, the security measures implemented to restrict cross-origin requests, and the attacker's knowledge and motivation. However, given the prevalence of CSRF attacks and the potential impact on data security and user privacy, the risk associated with Insecure CORS Policy is significant if not properly mitigated.

Steps to Reproduce:

  1. Identify endpoints or resources within our application that are accessible via cross-origin requests.
  2. Analyze the Access-Control-Allow-Origin header configuration to determine if it allows requests from untrusted origins or uses wildcard (*) to allow requests from any origin.
  3. Attempt to send cross-origin requests from unauthorized origins to access sensitive resources or perform unauthorized actions.
  4. Determine if attackers can exploit Insecure CORS Policy vulnerabilities to bypass access restrictions and manipulate sensitive data within our application.

Recommendations for Developers:

  1. Implement Whitelisting: Configure the Access-Control-Allow-Origin header to only allow requests from trusted origins explicitly, rather than using wildcard (*) or allowing requests from any origin.
  2. Use Credentials with Caution: When allowing credentials (cookies, authorization headers) to be sent with cross-origin requests, ensure that the Access-Control-Allow-Origin header is not set to wildcard (*) and restricts access to trusted origins only.


Addressing Insecure CORS Policy vulnerabilities is critical to protecting against CSRF attacks, data theft, and unauthorized access to sensitive resources within our application. By implementing proper CORS policies and restricting cross-origin requests to trusted origins, we can mitigate the risks associated with Insecure CORS Policy and enhance the overall security posture of our systems.