title: A potentially dangerous Request.Path value was detected from the client (?)
body: <p><strong>Environment</strong>:</p>
  
  <p>IIS 8.5</p>
  
  <p>.NET Framework Version: 4.6.2 (using WebForms)</p>
  
  <p>Windows Server 2012 R2</p>
  
  <p><strong>Problem:</strong></p>
  
  <p>The following exception is being reported:</p>
  
  <pre><code>BASE EXCEPTION: System.Web.HttpException (0x80004005): A potentially dangerous Request.Path value was detected from the client (?).
     at System.Web.HttpRequest.ValidateInputIfRequiredByConfig()
     at System.Web.HttpApplication.PipelineStepManager.ValidateHelper(HttpContext context)
  
  BASE EXCEPTION HRESUT: -2147467259
  
  EXCEPTION: System.Web.HttpException (0x80004005): A potentially dangerous Request.Path value was detected from the client (?).
     at System.Web.HttpRequest.ValidateInputIfRequiredByConfig()
     at System.Web.HttpApplication.PipelineStepManager.ValidateHelper(HttpContext context)
  </code></pre>
  
  <p>Other information shown in our logs:</p>
  
  <pre><code>PATH_INFO
  /cities/index.aspx?locid=4163
  ----
  QUERY_STRING
  ----
  REMOTE_ADDR
  66.249.65.204
  ----
  REMOTE_HOST
  66.249.65.204
  ----
  REQUEST_METHOD
  GET
  ----
  SCRIPT_NAME
  /cities/index.aspx?locid=4163
  ----
  URL
  /cities/index.aspx?locid=4163
  ----
  HTTP_FROM
  googlebot(at)googlebot.com
  ----
  HTTP_USER_AGENT
  Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
  </code></pre>
  
  <p>What I do not understand is if I cut and paste the path in my browser, the page is rendered just fine and without error.</p>
  
  <p><strong>Questions:</strong></p>
  
  <ol>
  <li>Why does googlebot, when crawling the page produce this error, yet no error is generated when I enter the path in a browser?  (I do find it odd that the error log shows no value for the query string, even though it is present).</li>
  <li>Why is the "?" character considered potentially dangerous?</li>
  </ol>
  
  <p>Any advice would be appreciated as I am trying to understand how this particular "error" is being raised when the path is in fact valid.</p>
  
  <p>Thanks in advance.  </p>