User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:99.0) Gecko/20100101 Firefox/99.0

Steps to reproduce:

1. Open firefox
2. Try to drag & drop files to webpage (nextcloud, owncloud etc.)
3. Nothing happens and files are not uploaded

--> With chromium and dolphin drag & drop works as expected so it seems, that it is either a firefox-flatpak issue or a firefox issue.

Actual results:

Files are not dropped into the webpage from dolphin.

If I try to drag & drop say a png firefox says that the file cannot be found (although it is for sure there).

If I drag and drop a file from say /run/user/1000/doc/dde691b8/Downloads/ it works as expected. But not with the "normal" paths to files.

Expected results:

Upload starts. Files get dropped into ff.

mozilla-flatpak - 1.0
Operating System: Kubuntu 22.04
KDE Plasma Version: 5.24.5
KDE Frameworks Version: 5.94.0
Qt Version: 5.15.3
Kernel Version: 5.15.0-33-generic (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-8565U CPU @ 1.80GHz
Memory: 15.3 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 620

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Gtk' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Do you see the issue with plain Mozilla binaries?
https://fedoraproject.org/wiki/How_to_debug_Firefox_problems?rd=Bug_info_Firefox#Testing_Mozilla_binaries
Thanks.