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# Unsanitized user input in Access-Control-Allow-Origin

## Overview

* **Rule ID**: `javascript_express_insecure_allow_origin`
* **Applicable Languages**: Javascript
* **Weakness ID**: CWE-346

## Description

Using unverified user-defined input to set the Access-Control-Allow-Origin header can result in unauthorized access to sensitive data. This vulnerability exposes your application to potential security risks by allowing attackers to specify origins that can access resources.

## Remediation Guidelines

* **Do not** define the `Access-Control-Allow-Origin` header with user input. This practice can compromise the security of your application by allowing data access to unintended users.
* **Do** verify user input if it is absolutely necessary to use it for defining origins. Ensure that the verification process is robust to prevent security breaches.
* **Do** use a safelist approach when specifying origins. This uses a predefined list of trusted origins and only allows requests from those origins.

## References

* [**OWASP Origin & Access-Control-Allow-Origin**](https://owasp.org/www-project-web-security-testing-guide/latest/4-Web_Application_Security_Testing/11-Client-side_Testing/07-Testing_Cross_Origin_Resource_Sharing)
* [**CWE-346: Origin Validation Error**](https://cwe.mitre.org/data/definitions/346.html)
* [**OWASP Top 10: A07:2021 - Identification and Authentication Failures**](https://owasp.org/Top10/A07_2021-Identification_and_Authentication_Failures/)

## Configuration

To omit this rule during a scan, and to provide you with continuous 24/7 code-level scanning, you can employ our [**SAST TOOL**](https://scopy.sec1.io/login)