How to find out who last updated a record through the Customer Portal?

The ModifiedByExt field reflects the name of the customer who last updated the record through the Customer Portal.
Follow these steps to view who modified the record:

1. Log in to your CRM account.
2. Click the Main Menu.
3. Go to the respective module (e.g., Cases, Deals, Contacts). The List View of the module opens. 
4. Open the record created by the partner. The Summary View of the record opens.
5. Go to the Details View.
6. Got to the ModifiedByExt field to see the customer’s name who modified the record.

Note: If the customer contact is deleted, the system will display strike-through text in this field.