Firefox 98 is released today (2022 March 8th) and they messed with downloading. It looks to me like this is a potential danger zone for inexperienced users… with the potential to accidentally tell Firefox to always open certain files. (Who actually wants this option that isn’t smart enough to add in a download manager add-in??)
I have my Firefox set to always ask where to save a download, so I am somewhat protected from this automation. I just opened up about:config and then toggled the setting
browser.download.alwaysOpenPanel to off so that there is no accidental clicks enabling anything automatically.
The Firefox 98 release notes are here:
And the download specific change notes: