Hi k.y.tushkov, Firefox 40 was released in August 2015, and I have not heard about a general problem uploading MS Office documents before. It could be that your DMS is particularly sensitive to the content-type indicated by Firefox during upload.

When Firefox is first installed, it checks the Windows registry for the MIME types associated with different file extensions. However, over time, Firefox learns new associations and occasionally will use a new INCORRECT association when uploading a document. We usually see this occur with PDF files.

The usually effective workaround for that problem is to remove the user's current mimeTypes.rdf file and have Firefox generate a new one. The steps are listed in these threads, for example:

• not allowing PDF attachments in Gmail
• Pdf files uploaded with Firefox 45 marked as unknown in Google Drive

Hi jscher, I used by your recommendation, however, it still doesn't work. Where and how can I check what kind of information about the uploaded file is been sending by Firefox?

I think the information is difficult to see when you are uploading because it is not displayed anywhere on screen. Possibly it might be displayed by the developer tools but I have not investigated that because I can't immediately think of any sites for testing.

Thanks for quick enough answer, Jefferson. But I have to be sure that the problem isn't linked to the browser for sending the request to the IT support of the development company.

Who can help me with that? I meant with the understanding of the possibility to get the needed information.

This question is very important for me. So, I'm looking forward to getting the answer ASAP.

Hi Konstantin, if the company says Firefox is sending its server a different header than other browsers when they test it, they are probably correct about that. Can they detail exactly what the difference is, whether they have submitted a bug report, and/or why they aren't able to work around it?

I'm not sure that they did it. if I understood you correctly the better way is that company will send you a bug report. I'll ask them about it then

Where will be better to post their report: at that post or to create another one?

It is best if they file on

https://bugzilla.mozilla.org/enter_bug.cgi

and let you know the bug number so we can take a look at it.

Maybe check the MIME database key in the Windows registry.

You can check specific file extension keys (e.g. .jpg) in the registry with the registry editor.

• HKEY_CLASSES_ROOT\.xxx

You can check a possibly linked MIME type in the MIME Database registry key.

• HKEY_CLASSES_ROOT\MIME\Database\Content Type\

cor-el said

Maybe check the MIME database key in the Windows registry. You can check specific file extension keys (e.g. .jpg) in the registry with the registry editor.

• HKEY_CLASSES_ROOT\.xxx

You can check a possibly linked MIME type in the MIME Database registry key.

• HKEY_CLASSES_ROOT\MIME\Database\Content Type\

All of those keys are correct.

Hi, all again.

That company said that they sent the [[bug report|https://bugzilla.mozilla.org/show_bug.cgi?id=1324421]]

Hi Konstantin, thank you for the update.

Completely unrelated mime types like "application/save" are usually caused by information added to mimeTypes.rdf as files are downloaded. My longstanding profile has accumulated these associations for the .xls extension:

• "application/vnd.ms-excel" - official content type
• "application/x-unknown" - lazy site identification
• "application/excel" - mistaken site identification

In a fresh test profile, mimeTypes.rdf doesn't have any preset association for the .xls extension.

Hi Jefferson, Talking about the mime types, I cleared whole profile of Firefox on my computer by clicking the button 'Clear Firefox' on the page 'about:support'. It doesn't help me to avoid the problem with our system.

I really want to attach my mimeTypes.rdf to that question, but I didn't find how to do that.

And, could you explain to me where I can find the strings which were mentioned by you in the previous message? I haven't found it on my mime file.

P.S. in the bug report, you suggested using the 51st version of Firefox or above. But I have the only 50th version and it talks me that any update unavailable.

Hi Konstantin, if your mimeTypes.rdf does not have any instances of this string --

NC:fileExtensions="xls"

-- then Firefox should be fetching the content type from the Windows registry. If that continues to have the same problem, then the fix in Firefox 51 (currently in beta) might not help.

To test with without disturbing your current Firefox installation, you could use the "Portable" version. That installs into and runs from its own folder. More info: http://portableapps.com/apps/internet/firefox_portable/test

Hi Jefferson, I really can't find any strings which contain something like 'xls' on my mimeTypes.rdf file.

If I understood you correctly, you suggested me to try the portable version of FireFox for checking the situation with possibly the incorrect uploading files, didn't you?

If you could, yes, test Firefox Beta (future Firefox 51) using the portable version (to avoid interfering with Firefox 50).

I tried to install -- it really sounds strange -- the portable version of Firefox. But I couldn't do it because the installer told me that I need to select the correct folder for the installation (see the attachment) What was wrong?

Maybe because it's a 32-bit installer and you need to use c:\Program Files (x86)\ ? Or it could be a permissions problem. I just run it out of Downloads since it's temporary anyway.

Hi Jefferson, the problem had repeated while I was working with the portable version of Firefox. Could I check something for understanding what is going on? I mean some file of portable Firefox or something else.

P.S. I'm sorry. That happened with documents which were made early.

If Firefox Beta (Firefox 51) does not upload new files correctly, then the bug fix I mentioned earlier does not fix the bug you're experiencing. I don't think anything will fix the problem for previous uploads; once the site has stored incorrect file type information, the edit would need to be on the site's end.