Windows 7 File Extension (Bug?)

I noticed a strange behavior in Windows 7 today, that was not replicated in Windows Vista or XP.  It isn’t a vulnerability, just a strange behavior.

If you have Windows 7 try the following:

  1. Open a folder that contains at least one file.
  2. Rename the file so the extension ends in a . (test.txt becomes test.txt.)
  3. Hit Yes to accept changing the file extension
  4. The file is now gone.
  5. Either hit F5, right click and select Refresh, or go to a different folder and come back.
  6. Your file will be there again, with the ORIGINAL file extension.


So this begs the question… where did the file go? Why was the screen not refreshed to show it appearing again, and is this possibly exploitable to hide files with?

UPDATE 1 (4/12/2011 1:50pm):

Trying to find where/how to submit Windows 7 bugs is a pain.  I have submitted this finding to Steve Gibson (Security Now) since I was getting frustrated, as well as the Windows 7 Blog ( is a bounce, and I refuse to call tech support and be charged for trying to help.

UPDATE 2 (4/12/2011 2:03pm):

 Steven Sinofsky (@microsoft) replied back to my email to the forum post “Thank you.”  Hopefully this means someone will look into this, and keep me in the loop of the progress/resolution!

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