Pterodactyl has a Reflected XSS vulnerability in “Create New Database Host”

[!NOTE] Message from the Pterodactyl team:

The Pterodactyl team has evaluated this as a minor security issue but does not consider it something that should be assigned a CVE, nor does it require active patching by vulnerable systems.

This issue is entirely self-inflicted and requires an administrative user paste an obviously incorrect value into a database host field, submit it, and run into the XSS when the error message is rendered. However, we have determined that this fix is good security hygiene and may prevent issues in other areas not yet discovered.

Summary

When an administrative user creates a new database host they are prompted to provide a Host value which is expected to be a domain or IP address. When an invalid value is encountered and passed back to gethostaddr and/or directly to the MySQL connection tooling, an error is returned. This error is then passed back along to the front-end, but was not properly sanitized when rendered.

Therefore it is possible for an admin to knowingly paste a malicious payload such as <script>prompt(document.domain)</script> into the Host field and XSS themselves.