How about Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. Install Final Release Version of 57.0.4 at www.mozilla.org/firefox/all/

It will be on the Mozilla Servers tomorrow as a full download/update. So can mess around in 56 for days. Jump ahead and hope to fix it since not getting any solutions as of yet after all these hours. Note : Legacy Extensions will be disabled and or removed.

Please let us know if this solved your issue or if need further assistance.

edit: replaced the unofficial betanews link for current Release. Mozilla does not send out new Release to other sites early as they just jump the gun.

Thanks PK, I've already de-installed Firefox and all the related files, and re-installed fresh, with no luck. I will wait for the beta you've mentioned to be available officially, and try that.

Akkirman said

Thanks PK, I've already de-installed Firefox and all the related files, and re-installed fresh, with no luck. I will wait for the beta you've mentioned to be available officially, and try that.

It is not the Beta It is the Full Final Release the site always gets it a day early before it goes on the Mozilla servers. This is my daily fix site for software for last 15+ years so ya is good place.

Thanks again, will try and report back :)

Un-installed v.56, and deleted, including all the Firefox files in system library. Emptied Trash. Re-started iMac, installed v57 clean. Problem continuing. Downloaded my own photos from my Facebook page via Firefox, and when I check file info, Nikon Capture is shown as the default app to open it. I changed it to PS6, clicked save as default, next download via Firefox, same problem all over again :)

Is Firefox modifying the file name extension, for example, from .jpg to .jpeg or something else that isn't standard?

I wonder if it's worth asking on an Apple forum whether this is a known issue?

jscher2000 - no visual modifications to the file name, or the extension. No problems with Safari or Chrome. In the past never had any problems with Firefox (use to use it as my default browser). This problem appeared only after updating to v56. I'm a heavy user, but don't use any extensions or plug-ins. I'll try the Apple forum later tonight.

Latest - If I drag and drop the photo into one of my folders the problem exists, however if I right click and use the "Save Image As..." from the drop down menu to download then it works fine and my default app is not overridden by Firefox.

Akkirman said

Latest - If I drag and drop the photo into one of my folders the problem exists, however if I right click and use the "Save Image As..." from the drop down menu to download then it works fine and my default app is not overridden by Firefox.

Your reply reminded me of a change in Google image results that caused drag-and-drop to save a link to the online address of the image rather than the actual image itself. That started coming up in August. For example: https://support.mozilla.org/questions/1170552. I don't know if that is what is happening on yours or something new.

Does sound similar. I tried drag-and-drop from Google, and works fine in my case.

I have the same thing going on. After dragging and dropping a jpg onto the desktop, the file extension remains, but the default app chosen to open jpgs (in my case, Preview) has changed (in my case, to Digital Photo Professional). A real headache, since I have to go back and reset the default every time for jpgs to open in my preferred app. No problems when using Safari, so it seems to be a Firefox issue.

Instead of drag-and-drop, I've been using (Mac OS) right click then "save image as", which seemed to get around the problem. Now with v57.04 the problem seems to have gone. I can drag-and-drop. Hope this helps :)

Akkirman said

Instead of drag-and-drop, I've been using (Mac OS) right click then "save image as", which seemed to get around the problem. Now with v57.04 the problem seems to have gone. I can drag-and-drop. Hope this helps :)

Thanks for the tip. Regarding v57.04, that's what I am currently using and it is still misbehaving. Maybe I need to do another reset or refresh.

Hi 3ringcircus, if a file is saved to the desktop/downloads with its true extension and MacOS has associated the wrong application, there's probably a way to set Preview as the default application to open that type of file instead. I'm not familiar enough with MacOS to know how you do that. I would check into that first instead of Refresh; I don't see how Refresh would help.