A forecast user is given viewer access to their manager's forecast with the Edit own and Reports Forecast rights. They then attempt to apply a forecast override to their own forecast and hit an error

This generates an error on the front end: There was an error loading this page and generates a logged message: "SECURITY: Illegal access by user <uid> to override forecast for {\"type\":\"FORECAST_ROLE\",\"userId\":<uid>,\"userType\":\"OWNER\"}.","userId":"<uid>","orgId":"<oid>"

It is not permitted to impersonate a higher level forecast role than your own to update your own forecast figures