Umbraco forms The qualys security scan is appending items to the formId and theme on the umbraco forms causing verbose errors.

Although I have a custom 500 page there its able to get through to the YSOD.

Is there any way to 1) Stop the formId and Theme from being editable (Ive tried editing the render and making them disabled but that stops the form working)

2) Clean these fields on submit

My 500 page is set up as follows

  <system.web>
<customErrors mode="Off" redirectMode="ResponseRewrite" defaultRedirect="~/500.aspx">
    <error statusCode="400" redirect="~/400.aspx"/>
    <error statusCode="404" redirect="~/404.aspx"/>
    <error statusCode="500" redirect="~/500.aspx"/>
</customErrors>

   System.webServer
          <httpErrors errorMode="Custom" existingResponse="Replace" > 
              <remove statusCode="404" subStatusCode="-1" />
                 <remove statusCode="500" subStatusCode="-1" />
                <error statusCode="404" path="404.html" responseMode="ExecuteURL"/>

                <error statusCode="500" path="500.html" responseMode="File"/>
        </httpErrors>

  <location path="media">
        <system.webServer>
            <httpErrors errorMode="Custom" existingResponse="Replace">
                <remove statusCode="404"/>
                <error statusCode="404" path="404.html" responseMode="File"/>
            </httpErrors>
        </system.webServer>
    </location>