The DetailsView control on the ShowPoliciesAndClaimsExercises.aspx web form has been modified in this way. To see the effect, search for a valid policy holder name such as 'babbage', show their policies and claims, then change the policy holder details.
FindPolicyHoldersExercises.aspx
The ASP.NET markup for the DetailsView control includes lines such as:
<asp:BoundField DataField="accountNumber" HeaderText="accountNumber" SortExpression="accountNumber" ReadOnly="True" />