Remediating CORS Violations

Cross-Origin Resource Sharing (CORS) Violations are scanned as part of the Security Misconfiguration Vulnerabilities Security Tests used to evaluate the Web Application Security Risk Vector.

Cross-Origin Resource Sharing (CORS) allows site A to give permission to site B to read data from site A using the visitor's browser and credentials. This security test assesses whether CORS requests made by the web application are being blocked due to misconfigured or overly restrictive CORS headers. We count unique error messages per domain to identify issues with how cross-origin requests are handled.

Need to fix?

• Review CORS violation messages in your browser’s developer tools (Console tab).
• Check your server’s Access-Control-Allow-Origin header. Avoid using the wildcard (*) unless absolutely necessary.
• Set CORS permissions to only allow trusted domains.
• Remove or update any third-party content that may be causing violations.
• Regularly review and update your CORS policy as your application changes.

How can I check for CORS Violations in my web application? Use Chrome Developer Tools (Console) to inspect for CORS-related errors. Verify your server's Access-Control-Allow-Origin and other related headers (e.g., Access-Control-Allow-Methods, Access-Control-Allow-Headers).

What is the risk? Improperly configured CORS headers can:

• Break critical cross-origin functionality, including loading resources from APIs or CDNs;
• Lead to silent failures in JavaScript execution;
• Result in degraded application functionality or unexpected behavior for end users.

Does this impact my WAS Risk Vector Grade? Yes.

Possible Grades:

• Good: Weight = 0.
• Fair: At least one unique CORS violation. Weight > 0 and 1.

What will I see in the portal?

Details: The webpage contains content that violates the browser’s Cross-Origin Resource Sharing (CORS) policies. The presence of such errors represents a latent reflection that:

• The website content and security policies are incongruent.
• The website is unknowingly including certain third-party content.
• Malicious code is injected into the website (but blocked by policy).