Firefox recognizes download file type as text regardless of content type response header
I have Firefox ESR 52.9.0 (32-bit) installed on Windows XP. When I download a file, it always recognizes it as text and adds a "txt" extension to it. This is done regardless of the server's HTTP response headers, indicating the file type as either "application/octet-stream" or "application/vnd.ms-access" or anything else for that matter.
Same version on different operating systems may differ in behavior. I tried uninstalling and re-installing and removing all plugins/extensions but it doesn't seem to make a difference.
Additional System Details
- User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36
Here are screenshots from same version of browser on two different operating systems.
Prior to helping you here I'd strongly encourage you to upgrade to a supported operating system, per https://support.microsoft.com/en-us/lifecycle/search?alpha=Microsoft%20Windows%20XP%20Service%20Pack%202 the version you currently use ceased to be supported on 4/8/2014.
https://distrochooser.de/en/ is generally a good starting point to find an alternative.
Once that is taken care of, please also update the version of Firefox ESR per https://www.mozilla.org/en-US/firefox/68.1.0/releasenotes/
If you still can reproduce the issue then, please let us know here and we'd be happy to help.
Please excuse me but I strongly believe that continuing to use unsupported well known vulnerable versions of both the OS and browser is a disservice to yourself and harmful for the web as a whole.
Some browser versions are beyond our control. However, this also happens with 68.0.2 on Windows 10.
Could you please share a URL where this can be reproduced?
Have you tried https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode yet?
Unfortunately I cannot share the link, as it is our business product which requires username/password. I did try starting Firefox in safe mode (without any plugins/extensions) but it didn't make a difference.
Please review https://support.mozilla.org/en-US/kb/change-firefox-behavior-when-open-file#w_changing-download-actions it might be you ought to add the content type on Firefox.
Please let us know if this solves your question.
Unfortunately, it doesn't. I don't see the content type there, which may be the problem. However, I don't see a way of editing this and adding a new content type, which may very well solve the issue.
You can inspect the MIME database key with the registry editor (regedit.exe) and do a search for that MIME type (file extension) via Ctrl+F. Be cautious with editing the registry as there is NO UNDO possible: all changes are applied immediately. You can export key(s) in the registry editor before making changes. You can check specific file extension keys (e.g. .mdb) in the registry with the registry editor.
You can check a possibly linked MIME type in the MIME Database registry key.
- HKEY_CLASSES_ROOT\MIME\Database\Content Type\
Thanks, I was afraid that was the solution. However, this is too "invasive", and clients' browsers are beyond our control.
On your Firefox 68 installation, you can use my extension to log the content-type headers sent by the server:
Click the Zzzz button to start logging; that also enables a drop-down menu to view the log (Add/Edit).
If the server is sending text/plain, that probably means the .mdb extension is not mapped to a content type. I assume it must be a Linux server, since I'm pretty sure Microsoft IIS would have that mapped?
For Apache or similar, you define new content types using AddType.
Depending on your hosting, you may need to use .htaccess if you can't update the central config files.