The Booking for Appointments and Events Calendar – Amelia (Premium) plugin for WordPress is vulnerable to Privilege Escalation in versions 8.0 - 9.6.2. This is due to insufficient validation of the attacker-controlled 'type' parameter in the customer update endpoint, which allows customers to set their role to 'manager' and trigger creation of a WordPress user with the wpamelia-manager role when the 'externalId' parameter is set to 0. This makes it possible for unauthenticated attackers to escalate their privileges to administrator by first elevating to the manager role, then creating a provider entity linked to an administrator user ID and overwriting that administrator's password.

The Amelia Premium plugin for WordPress (versions 8.0 to 9.6.2) contains a critical privilege escalation vulnerability tracked as CVE-2026-9055. The flaw stems from insufficient validation of the attacker-controlled 'type' parameter in the customer update endpoint. An unauthenticated attacker can exploit this by first elevating their role to 'manager' via the customer update endpoint, then creating a provider entity linked to an administrator user ID to overwrite that administrator's password. This two-stage attack chain allows full administrator-level compromise of the WordPress installation. The vulnerability is triggered when the 'externalId' parameter is set to 0, causing creation of a WordPress user with the wpamelia-manager role. No authentication is required to initiate the attack, making this a significant risk for any site running the affected plugin versions.