Recently, UI extension fields that can be set to ‘Internal’ (by means of a checkbox named ‘Visible only to specialists, auditors, and account administrators of this account’) were made ‘Internal’ by default, following the principle of Security by Default. For users who can see such a field in their account, it was, however, not clear that users from other accounts would not be able to see that field. It is now.
Ticking the checkbox (as in the example above) generates a UI extension field with a lock icon, making it clear to the user that this field is internal to an account the user has a Specialist role in. Hoovering the mouse pointer over this icon displays the account the field is internal to.