Open redirect in Mautic/core

An Open Redirect vulnerability exists in the public form submission endpoint (/form/submit) of Mautic. After a form is submitted, the application redirects the visitor to a return address supplied with the submission without verifying that it points to the Mautic instance or another trusted host. An unauthenticated attacker can exploit this to send visitors from a legitimate Mautic domain to an arbitrary external website, for example to phishing pages that imitate the original landing page or to sites that deliver malware. Any Mautic instance with a published form is affected. Exploitation requires the victim to submit a form prepared by the attacker.