Task "Modified by" and "Started by" fields show the application identity rather than the logged in user.
The customer is running a task but the task "started by" has the service account in the field instead of the user account. The customer is logged in with his account.
The IIS TaskManagement virtual application had anonymous access enabled
ITMS 7.6-8.x
Disable anonymous access on the Taskmanagement virtual application in IIS: