Shoud be fine to have a JS object in confirmation page that exposes attendee's data (at last the email address) in oder to track user activity on other Marketing Platforms (ie Sendinblue). Using would be possible to trigger JS events, start automaton workflow of any other thing on remote server: Example: a user register to a webinar, on confirmation i can identify him on newsletter system and trigger an automation, a retageting campain or an SMS campaign (if the user is registered on my mailing system of course)