Hi soowon.yi, when you use a basic file input control to choose file from Windows, you should get an Open File / File Upload dialog opening. But you don't get that, nothing happens?

Or if the dialog opens, the selected file isn't return to the page successfully?

Could you try:

New Profile Test

This takes about 3 minutes, plus the time to test some file inputs.

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it.

Click the "Create a New Profile" button, then click Next. Assign a name like Nov2019, ignore the option to relocate the profile folder, and click the Finish button.

After creating the profile, scroll down to it and click the Launch profile in new browser button.

Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system so we can get a clean test.

Does the File Upload window work any better in the new profile?

When you are done with the experiment, you can close the extra window without affecting your regular Firefox profile. (Nov2019 will remain available for future testing.)

After you have completed the experiment:

When you create a new profile, Firefox sets the new profile as the default.

Simply return to about:profiles Below your original profile select Set as default