The Secure guest user record access setting was enabled in all Salesforce orgs with communities or sites in Summer ’20, but could still be disabled during that release. In Winter ’21, this setting is enabled in all orgs and can no longer be disabled. The Secure guest user record access setting enforces private org-wide defaults for guest users and restricts the sharing mechanisms that you can use to grant record access to guest users.
Where: This change applies to orgs with active communities and sites in Essentials, Enterprise, Performance, Unlimited, and Developer editions.
When: The timelines for the rollout and enforcement of this setting are published in Guest User Security Policies and Timelines.