CVE-2026-52838: Easy!Appointments disable_booking_message rendered as raw HTML on public booking page — Stored XSS

Easy!Appointments allows administrators to define a custom “booking disabled” message through the booking settings page. That value is stored in the disable_booking_message setting via a rich-text editor and later passed directly to the public booking_message view without escaping or sanitization:

<p><?= vars('message_text') ?></p>

An authenticated administrator can store HTML or JavaScript in this field, enable disabled-booking mode, and trigger stored XSS in every unauthenticated visitor who opens the public booking page.