Disable drag&drop uploads in Firefox

public static string SanitizeMessageInput(string message)
{
   HtmlDocument doc = new HtmlDocument();
   doc.LoadHtml(message);

   if (doc.DocumentNode != null)
   {
      HtmlNodeCollection imageDataNodes = doc.DocumentNode.SelectNodes("//img[contains(@src,'data:')]");
      // strip out BASE64 encoded images in the message
      if (imageDataNodes != null)
      {
         foreach (HtmlNode node in imageDataNodes.ToList())
         {
            if (node.Attributes["src"].Value.IndexOf("base64,") >= 0)
            {
               node.ParentNode.ReplaceChild(HtmlNode.CreateNode("<div class=\"tinyerror\">Inline Image removed from message, don't drag images into the message editor!</div>"), node);
            }
         }
      }
      // you can do more processing here to also strip out script tags and the like
      return doc.DocumentNode.OuterHtml;
   }
   else
   {
      return message;
   }
}