On Mon, 18 May 2026 at 22:01:16 -0400, Aaron Rainbolt wrote: Of these two, org.freedesktop.portal.OpenURI.OpenFile is probably more problematic. This is because access to the OpenURI portal seems to be implicitly allowed by Flatpak. Expanding on what Flatpak intends to allow here:

If all applications followed the xdg-mime manpage's advice to never execute code when opening a file, this wouldn't be that big of a problem. This is where Wine comes in; it ships a desktop file that registers Wine as a MIME handler for 'application/x-ms-dos-executable', 'application/x-msi', and 'application/x-bat'.

Unfortunately, I was able to find another program with an unsafe handler registered just while writing this email (which I intend on reporting privately once I've sent this). So while it seems like these kind of handlers aren't super common, they aren't that hard to find if you dig around for a while.

We're working on a sandboxing system (really a glorified systemd-nspawn frontend) that allows each sandbox to be self-sufficient enough to not need access to the host's D-Bus daemon. [9] That should prevent any possible way to leverage D-Bus as a sandbox escape mechanism.

smcv