Security, why does the Transmission Flatpak require filesystem=host permissions?

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Hi everyone,

I’m currently auditing the permissions of my installed Flatpaks on Fedora Silverblue. I noticed that Transmission (com.transmissionbt.Transmission) comes with the following permissions by default:
filesystems=xdg-run/gvfsd;host;

As a Silverblue user, I am concerned about the security implications of a BitTorrent client, which is constantly connected to thousands of external peers, having full host access to my entire home directory and system.

My questions for the community are:

  1. Is there a technical reason why host is required instead of just xdg-download?
  2. Does xdg-run/gvfsd imply that the app can monitor my network mounts and cloud drives?
  3. If I revoke these via Flatseal and only grant access to ~/Downloads, will I break core functionality (like magnet link handling or resume-on-reboot)?

I feel that for an immutable, security-focused OS, we should be pushing for the “Principle of Least Privilege.” I’d love to hear if others have successfully hardened their Transmission setup or if these broad rights are a known necessity.

Thanks!

2

It should be okay to give access to ~/Downloads only.

Most Flatpaks are not designed with security or PoLP in mind, but rather with usability (you may want to store your downloaded files anywhere rather than just in your Downloads dir).

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Better yet, xdg-download/torrents:create. Then set the default download location in the app to here. This makes it so that it can access none of your other files in Downloads.

  • xdg-download is a shortcut to the downloads location, which is typically ~/Downloads unless you manually changed it
  • :create tells flatpak to automatically create this folder location when you start the app.
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