Current State:

With the introduction of Assets Macro : Showcase your Assets objects in Confluence Cloud.Assets details can be added to Knowledge Base Articles and customers can view from Portal.

However when the "Key" Column is added in results and customers clicks on it , page redirects to Customer Portal Home Screen.

When we click on "Key" , it gets navigated to the "Assets UI" with URL : https://<sitename>.atlassian.net/jira/servicedesk/assets/object/<objectID> 

Since User with customer role cannot access Assets Directly with above URL , user gets redirected to Portal.

Proposed Future State:

Either display a Modal Window to show more details about the Object or the Hyperlink should be updated based on the user context in portal.

Workaround:

The only workaround is to remove the "Key" column from Assets macro by customising the columns : Display your Assets data on a Confluence page