Shared users can't be edited in the application

Problem

When you try to edit a user in your application, you receive the following message:

Shared user can only be changed by himself/herself

Cause

Shared users that have the _WebLogin to multiple applications can only be edited by the user himself/herself.

Solution

Option #1
Use impersonation from Site Admin to log in as the user to the application, and then make the changes you want to do.

Option #2
Remove the user from any role that has _WebLogin enabled from Roles in the Admin menu.