Row-level data isolation in the admin
Magento’s ACL decides which admin screens a role can open, not which rows inside a shared grid it can see — so anyone allowed to view orders saw every business unit’s orders.
Overrode the collection classes behind each affected grid to apply website/store and split-attribute filters, tied to the admin user’s own scope.
Couples the module to Magento’s internal collection classes, so upgrades mean re-checking each override — kept in one module so there is a single surface to test.