FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. Prior to version 1.8.214, the Change Customer modal correctly hides out-of-scope customers through the mailbox-filtered search endpoint, but the backend conversation_change_customer action accepts any supplied customer_email. A low-privileged agent can forge a request and bind a visible conversation to a hidden customer in another mailbox. This issue has been patched in version 1.8.214.