To better protect your Salesforce org’s data, we restricted who can view record names in lookup fields. Users must have Read access to these records or the View All Lookup Record Names permission to view this data. This update also applies to system fields, such as Created By and Last Modified By. This update was first made available in Spring ’20.
Where: This change applies to Lightning Experience and Salesforce Classic in all editions.
When: Salesforce enforces this update in Spring ’21. To get the major release upgrade date for your instance, go to Trust Status, search for your instance, and click the maintenance tab.
Why: Admins have more control over what users see in records. Currently, users can view record names in lookup fields without Read access to those records.