Exception: System.Web.Util.FileUtil.CheckSuspiciousPhysicalPath(String physicalPath)

Error Time: ...
Machine Name: ...
Request URL: http://www.site1.com/page1|||RequestType:GET|||UserHostAddress:...|||UrlReferrer:
Error Message:
Error Source: System.Web
Error StackTrace:
at System.Web.Util.FileUtil.CheckSuspiciousPhysicalPath(String physicalPath)
at System.Web.HttpContext.ValidatePath()
at System.Web.HttpApplication.ValidatePathExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) ========================================

今天查看Live上的Log文件，看看有哪些异常。
看到如下这个错误，异常发生在System.Web.Util.FileUtil.CheckSuspiciousPhysicalPath(String physicalPath)

System.Web.dll中有如下代码

internal static void CheckSuspiciousPhysicalPath(string physicalPath)

{
  if (((physicalPath != null) && (physicalPath.Length > 0))
    && (Path.GetFullPath(physicalPath) != physicalPath))
  {
    throw new HttpException(0x194, "");
  }
}

还原异常
http://www.site1.com/page1%20