FF removes multiple spaces from file name on file download
When I download a file with multiple spaces in the name, like 'test space.txt' (there are 2 spaces between test and space), FF condenses the extra space into one, like 'test space.txt' (there is only 1 space between test and space). This happens on multiple websites and does not occur in other browsers.
It sounds as though it must be intentional. Is there a reason to preserve extra whitespace in the file name? If this is causing a problem, you could file a bug: https://bugzilla.mozilla.org/
By the way, since your Firefox reported itself to be version 78:
If you are using the Extended Support Release of Firefox 78, I suggest testing in the current Firefox Nightly, which likely will be the base for the next ESR. Issues unique to Firefox 78 are unlikely to get attention, so it would make more sense to file the bug against Nightly.
On the other hand, if this identification results from running Firefox 89 with privacy.resistFingerprinting enabled, you can ignore the above comment.