Issue: Mitre fields are in an unknown state for the admin user (alone) in the alert.alert index pattern. In all other places, the Mitre fields are indexed, even if it is a tenant user and in the alert.alert index pattern.
Fix: For the admin users belonging to the default tenant, the MitreAttackName and MitreID fields, have unknown field types, hence the appropriate field-description icon is unknown. This problem is due to the OpenSearch dashboard-cache and can be resolved by clicking on refresh icon located at Stack Management > Index patterns > alerts.alerts