Comment 4 for bug 1977679

I would expect that Firefox should show the dialog "What to do with file?" again if OS is not able to open the file regardless the option "Do this automatically from now" is ticked.
I guess Firefox nor OS cannot handle KML file itself. However the state "New tab is open again and again automatically" shouldn't occur because it could exhaust memory in worst case and it's also bad use experience to see neverending opening of new tabs.