What type of files are you talking about? This could be that your system as identified Firefox as the default program for those files.

Hi gciano, the .csv extension should remain associated with Excel. I would only expect to see that characterization if the extension was overridden to .html.

Do you routinely set Windows to show all file extensions so it's easier to confirm what Firefox did there? Since Microsoft pulled their support article on that, I now refer Windows users to this article instead: https://www.bleepingcomputer.com/tutorials/how-to-show-file-extensions-in-windows/

If all .csv files have become mistakenly associated with Firefox, I think you'll need to go through the Windows Control Panel to correct that, or there is a way to get Excel to re-register the extensions it cares about. See this thread: https://answers.microsoft.com/en-us/msoffice/forum/msoffice_other-msoffice_custom/cant-associate-microsoft-office-with-proper-file/42794017-9c45-45ff-8277-643661896450

Thanks, that's pretty helpful actually.

However, it seems like the problem is with .csv files: I'm setting default program in Windows to open them in Excel. However, in firefox options, there is no filetype for .csv

It's actually trying to open/save my download as FileName.csv.html

Any ideas?

gciano said

However, in firefox options, there is no filetype for .csv

Firefox learns as it goes for some file types. Mine has accumulated three different CSV content types (screenshot attached). Or maybe these were somehow absorbed from the system?

But the key thing is the content type, for example, text/csv, that the server sends Firefox. If the server sends a text/html type, then Firefox would normally guess that the file needs a .html extension.

If you have Firefox set to ask you where you want downloads saved (on the Options page, downloads section), then you have the opportunity to fix the file name when saving. For best results, you may want to set Windows to show you all file extensions. See: https://www.bleepingcomputer.com/tutorials/how-to-show-file-extensions-in-windows/