The Checkout Field Editor (Checkout Manager) for WooCommerce plugin for WordPress is vulnerable to Stored Cross-Site Scripting via custom radio and checkboxgroup field values submitted through the WooCommerce Block Checkout Store API in all versions up to, and including, 2.1.7. This is due to the prepare_single_field_data() method in class-thwcfd-block-order-data.php first escaping values with esc_html() then immediately reversing the escaping with html_entity_decode() for radio and checkboxgroup field types, combined with a permissive wp_kses() allowlist in get_allowed_html() that explicitly permits the <select> element with the onchange event handler attribute. This makes it possible for unauthenticated attackers to inject arbitrary web scripts via the Store API checkout endpoint that execute when an administrator views the order details page.