Easy!Appointments is a self hosted appointment scheduler. Versions prior to 1.6.0 correctly filter provider-scoped appointments in the "appointments/search" response, proving that provider isolation is an intended security boundary. However, the direct mutation endpoints "appointments/store" and "appointments/update" only check generic appointment privileges and never verify that the submitted "id_users_provider" belongs to the current session. A normal authenticated provider can inject new appointments into another provider's schedule via "store", or reassign existing appointments into a foreign provider's calendar via "update". The "store" path contains an additional write-before-crash bug: the unauthorized row is committed to the database before the controller crashes on a type error, so the attacker receives an error response while the foreign appointment is already persisted. Version 1.6.0 patches the issue.