For organizations which use custom data with an access control list (ACL) , backend users may use "Advanced Search" to discover implicit information from restricted fields.
CiviCRM v5.75 to v6.11
CiviCRM v6.12.0, v6.10.3 (ESR), and later
Upgrade to a fixed version of CiviCRM
Muhammad Shahrukh (Compuco), Coleman Watts (CiviCRM)
