Sails is an MVC style framework for building realtime web applications. Version 0.12.7 and lower have an issue with the CORS configuration where the value of the origin header is reflected as the value for the Access-Control-Allow-Origin header. This would allow an attacker to make AJAX requests to vulnerable hosts through cross site scripting or a malicious HTML Document, effectively bypassing the Same Origin Policy. Note that this is only an issue when `allRoutes` is set to `true` and `origin` is set to `*` or left commented out in the sails CORS config file. The problem can be compounded when the cors `credentials` setting is not provided. At that point authenticated cross domain requests are possible.

Affected: npm: sails

Affected versions of `sails` have an issue with the CORS configuration where the value of the origin header is reflected as the value for the `Access-Control-Allow-Origin` header. This may allow an attacker to make AJAX requests to vulnerable hosts through cross-site scripting or a malicious HTML Document, effectively bypassing the Same Origin Policy.

## Mitigating Factors

This is only an issue when `allRoutes` is set to `true` and `origin` is set to `*` or left commented out in the sails CORS config file.

The problem can be compounded when the cors `credentials` setting is not provided, because at that point authenticated cross domain requests are possible.

## Recommendation

Update to version 0.12.7 or later.

As this vulnerability is primarily a user error, the patch for the vulnerability will simply cause the application to write an error message to the console when a vulnerable configuration is used in a production environment.

Writing a proper CORS configuration is still the responsibility of the user, so it is necessary to check for the error message after installing the patch. Be sure you are not using `allRoutes: true` with `origin:'*'`, and that you uncomment `origin` and set it to a reasonable value. Ensure that if `origin` is set to `*` that you truly mean for all other websites to be able to make cross-domain requests to your API.

Likewise, ensure `credentials` is uncommented out and set to the appropriate value. Make sure to explicitly set which origin…