Easy!Appointments has server-side request forgery in CalDAV connection test that exposes the deployment's internal network

Caldav::connecttoserver at application/controllers/Caldav.php:60 hands the request's caldavurl to a Guzzle REPORT call without scheme or host validation. A logged-in backend user admin, provider, or secretary reaches loopback, RFC1918, and link-local hosts on the deployment's network. The Guzzle...