title: Firefox & HTTP Content-Disposition adds xlsx extension
body: <p>I have a .NET application which returns the following via HTTP</p>
  
  <pre><code>Cache-Control: private
  Content-Disposition: attachment; filename="ExportToExcel_14.09.2015 09:37:51.csv"
  Content-Length: 1515
  Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet; charset=utf-8
  Date: Mon, 14 Sep 2015 07:37:51 GMT
  Server: Microsoft-IIS/8.5
  x-powered-by: ASP.NET
  </code></pre>
  
  <p>However, firefox renames the file to <code>{filename}.csv.xlsx</code>. How can I turn this off? It causes problems because the file is a CSV, but I want users to be able to open it with excel. </p>
  
  <p><a href="https://i.stack.imgur.com/5vfuH.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5vfuH.jpg" alt="enter image description here"></a></p>