Today I received a docx document via Facebook. I tried to open it on my Mac. I couldn't open it "because it is from an unidentified developer". This surprised me. I've seen such alerts before when I open a newly downloaded program, but never for a document. So I right-clicked, selected "open" and then I got another alert if I was sure, and then I needed to give admin credentials.

Why does this happen? I've never seen this for pictures or PDFs I downloaded. Can you explain why this happens?

As SudoNinja explained in his answer, it's the OSX Gatekeeper functionality that stops executing newly downloaded programs with a warning. The question remains why Gatekeeper catches this file, which I have scanned with Google's VirusUploader.

  • 1
    It shouldn't happen what you have likely is not an actual word file
    – Ramhound
    May 28, 2014 at 22:14
  • Are you sure the message didn't refer to Word itself? Do you regularly use it?
    – Daniel Beck
    May 28, 2014 at 22:18
  • can you post a image ?
    – Devid
    May 28, 2014 at 22:38
  • I have Word 2008 (Mac) installed, use it rarely because I prefer Libreoffice. Double clicking the document resulted in opening Word 2008, which I don't want. So I opened the info window of the file and changed the standard application to LO. When I double clicked the document, the same happened for LO, so it's not a Word problem I guess. I checked the file with Google VirusUploader (which checks against 52 av-engines) and it was OK. I then entered admin credentials and could open the document.
    – SPRBRN
    May 29, 2014 at 12:08

4 Answers 4


That message is usually limited to executable files (programs), I would worry about some kind of malicious code in this case unless you absolutely trust the source. If you want to open it anyways right click and then 'open' will allow you to open it. Also, if you right click and see an option 'show package contents' its definitely not a word file, proceed carefully...


I've been having the same issue with a file that I created in Apple's Numbers.app (originally in Numbers '09 2.3, then migrated to 3.6.2).

I believe that Gatekeeper doesn't scan the file content. Instead, it looks for the presence of an extended attribute with the name com.apple.quarantine on the file.

$ xattr -l file.numbers
com.apple.quarantine: 0062;57472d09;Numbers;

I removed the attribute: see below. Before you do this, check that the file isn't malicious: see the other answers here for some advice. I don't know when or how the attribute was added to the file in my case, but I suspect it is a bug in OS X and/or the Numbers migration code.

$ xattr -d com.apple.quarantine file.numbers
(can now open the file without seeing the "unidentified developer" alert)

That error is from a piece of software called gatekeeper. It can be disabled in system preferences - security & privacy. The real question is what is the pdf trying to install. you might download sophos and give it a scan.


  • Thanks for the info! The document is scanned by Google and found safe as I explained in another comment. The real question is not what this docx document is trying to install, but why Gatekeeper catches this file?!
    – SPRBRN
    May 29, 2014 at 14:14

Apparently, Mac might have problem with *.docx file format and it thinks that it might be an application rather than a regular (text) file.

I experienced the same problem with opening *.docx files on my Sierra MacOS and after disabling gatekeeper I received the following message:

"“FILE.docx” may be an application. It was created by Pages and will be opened by LibreOffice. Are you sure you want to open it?"

(I'm quite certain that this file is a *docx file with text as I have created it by myself)

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