Something unexpected happened

Exception : A potentially dangerous Request.QueryString value was detected from the client (service="...ct">KULO4D</a>").

Reference : prod-cps-app1:638998200049119914

A potentially dangerous Request.QueryString value was detected from the client (service="...ct">KULO4D</a>").
   at System.Web.HttpRequest.ValidateString(String value, String collectionKey, RequestValidationSource requestCollection)
   at System.Web.HttpValueCollection.EnsureKeyValidated(String key)
   at System.Web.HttpValueCollection.GetValues(String name)
   at System.Web.Mvc.NameValueCollectionValueProvider.ValueProviderResultPlaceholder.GetResultFromCollection(String key, NameValueCollection collection, CultureInfo culture)
   at System.Web.Mvc.NameValueCollectionValueProvider.GetValue(String key, Boolean skipValidation)
   at System.Web.Mvc.ValueProviderCollection.GetValue(String key, Boolean skipValidation)
   at System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
   at System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor)
   at System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__0(AsyncCallback asyncCallback, Object asyncState)