CF7 to Webhook <= 5.0.0 - Unauthenticated Server-Side Request Forgery via CF7 Field Placeholder in Webhook URL Host

The CF7 to Webhook plugin for WordPress is vulnerable to Server-Side Request Forgery in all versions up to, and including, 5.0.0 via the pull_the_trigger. This makes it possible for unauthenticated attackers to make web requests to arbitrary locations originating from the web application and can be used to query and modify information from internal services. Exploitation requires that the admin-configured webhook URL contains a Contact Form 7 field placeholder in the host segment of the URL, and that the affected form is publicly accessible.