The Booking for Appointments and Events Calendar – Amelia plugin for WordPress is vulnerable to Stored Cross-Site Scripting via customer name fields in versions up to and including 2.2. This is due to an authentication bypass where the AddBookingCommand explicitly skips nonce verification (Command.php line 186), allowing unauthenticated users to submit booking data. While the plugin applies sanitize_text_field() to customer firstName and lastName fields (BookingApplicationService.php lines 302-308), this function only removes HTML tags and preserves special characters including double quotes. The vulnerability manifests in the administrative Calendar view where a FullCalendar eventContent callback interpolates customer names directly into JavaScript template literals (redesign/dist/index.js line 199) and renders them via innerHTML without proper HTML entity encoding. Because double quotes are preserved, an attacker can inject payloads like '" onmouseover="alert(document.cookie)"' to break out of the title attribute and inject malicious event handlers. This makes it possible for unauthenticated attackers to inject arbitrary web scripts that will execute when an administrator accesses the Calendar page and hovers over the malicious appointment.