Pimcore Admin Classic Bundle host header injection in the password reset

Pimcore's Admin Classic Bundle provides a backend user interface for Pimcore. The password reset functionality sends to the the user requesting a password change an email containing an URL to reset its password. The URL sent contains a unique token, valid during 24 hours, allowing the user to reset its password. This token is highly sensitive ; as an attacker able to retrieve it would be able to resets the user's password. Prior to version 1.2.3, the reset-password URL is crafted using the "Host" HTTP header of the request sent to request a password reset. This way, an external attacker could send password requests for users, but specify a "Host" header of a website that they control. If the user receiving the mail clicks on the link, the attacker would retrieve the reset token of the victim and perform account takeover. Version 1.2.3 fixes this issue.