IE 11 does not correctly decode the "filename" parameter of "Content-Disposition" HTTP header which uses "MIME encoded-word syntax" generated by an ASP.Net Handler

Not reproducible Issue #105912


Apr 27, 2014
This issue is public.
Found in build #
Reported by 0 people

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Steps to reproduce

URL = http://testä


Repro Steps:

  1. Visit this URL with IE 11, Firefox and Chrome: http://testä
    You will see that FF and Chrome are able to decode the “filename” value, where IE is not.
  • or, if the above URL is not available -
  1. Create an empty ASP.Net application with Visual Studio 2013.
  1. Add an generic ASP.Net handler ("testHandler.ashx", “testHandler.ashx.cs”).
  1. in testHandler.ashx.cs, add the source code from
  1. Run the handler in IE 11, Firefox and Chrome

Expected Results:

When sending the HTTP ‘Content-Disposition’ header with the value 'attachment; filename="=?utf-8?B?RmlsZSDDpMO2w7wudHh0?="’, IE should use “File äöü.txt” as pre-filled filename, instead of "=utf-8_B_RmlsZSDDpMO2w7wudHh0=".

Actual Results:


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    Comments and activity

    • Microsoft Edge Team

      Changed Assigned To to “IPBS P.”

      Changed Status to “Not reproducible”

      Changed Assigned To from “IPBS P.” to “Kris K.”

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