The Attribute Value Protection value of 'Use only secure subpages to protect attribute values on the list' works differently in 15.5.1 and 15.8.1. 

Steps to Reproduce:

1. Create a security group called, 'Test Group'
2. Add a resource to the security group
3. Create a Sub-page in Team Object called, “Admin” and set a Display Condition in the subpage as “Check Resource's Group = 'Test Group'”  ( checkGroup( "test_group", ctx, "EQUALS" ) )
4. Add the Team field, “Staff OBS Unit”( rsf_obsunit_id) to the Admin sub-page
5. Configure the Team field, “Staff OBS Unit”( rsf_obsunit_id) in the Team List Layout
6. Navigate to Object >> Team>> View >> Project Team - Staff  >> Options >> Set the Attribute Value Protection value as “Use only secured subpages to protect attribute values on this list”
7. Log into Clarity as a user who is not a part of the security group 'Test Group'
8. Navigate to Project >> Team and observe that Staff OBS Unit field

Results: 

• In Clarity Version 15.5.1.240, the Staff OBS Unit field is not editable
• In Clarity Version 15.8.1.238, the Staff OBS Unit field is editable

Release : 15.5.1

Component : CA PPM STUDIO

The results observed on 15.8.1 are the expected results. Secure Subpages are not available on the Team views, and Display Conditions do not determine if fields are editable or not. If the user is able to view the field on the list view, and he has the appropriate staffing access rights over the team record, he will be able to edit the field as well. 

The results being different in 15.5.1 appear to be the result of an old bug that has since then been fixed.