Amelia WordPress plugin: customers can export any event's attendee data

The Amelia plugin for WordPress is vulnerable to unauthorized access of attendee data due to a missing authorization check on the GetEventAttendeesCommandHandler::handle() function in versions up to, and including, 9.9.1. The handler only enforces the broad amelia_read_events capability — which the plugin's own wpamelia-customer role possesses — and does not verify that the authenticated user is an organizer/provider of the event referenced by the client-supplied id query parameter. This makes it possible for authenticated attackers, with wpamelia-customer-level access and above, to export the full CSV of attendee personally identifiable information (first/last name, email, phone, date of birth, gender, private notes, payment amounts/methods, WooCommerce order IDs, custom-field values, and uploaded-file URLs) for any Amelia event on the site by directly invoking the /report/event/attendees endpoint with an arbitrary event ID.