user is able to see item pages associated with category B, the role doesnot have those privileges

Setup > Workbench> Item Catalog Categories

Category A
Category B
Category C

The above are defined available.

Category A is associated with Item Pages A and View/Edit Privilege security A
Category B is associated with Item Pages B and View/Edit Privilege Security B
Category C is associated with Item Pages C and View/Edit Privilege Security C

Role A, B and C and simillarly group A, B and C are defined.

Role A has privileges to View/Edit only Item Pages Security A
Role B has privileges to View/Edit only Item Pages Security B
Role C has Privleges to View/Edit only Item Pages Security C