On 5/20/26 05:51, Simon McVittie wrote: On Tue, 19 May 2026 at 19:30:42 -0400, Aaron Rainbolt wrote: I wonder if it would be worth proposing a change to whatever system component handles opening files (probably something in Glib, or xdg-utils, haven't researched that deeply yet) It's a general-purpose specification that is designed to be implemented by an unlimited number of packages, some of them desktop-specific:
GLib, and via that, gio(1), xdg-desktop-portal and flatpak-xdg-utils' xdg-open(1) reimplementation some Qt/KDE library (I'm less familiar with the KDE world, so I don't know whether this is done in the Qt layer or somewhere in kdelibs) xdg-utils' xdg-open(1) (the reference implementation of that name) Debian's mailcap package, which translates fd.o MIME handlers into traditional mailcap(5) handlers web browsers like Firefox and Chromium might reimplement it? not sure ...
so any change to how the spec is to be implemented would have to be fd.o consensus and spread across all of those. Honestly, I think the open-ended nature makes it inherently insecure.
Sandboxes should only allow allowlist of file types and make everything else fall back to a safe default. This could be a simple text editor (no IDE support!) for text files, and a hex editor (or an error) for binary files. -- Sincerely, Demi Marie Obenour (she/her/hers)
Hi, Security Note: Never set a handler that will blindly execute code or commands from the file being handled. Such behaviour will sooner than later lead to unintended code execution i.e. through a curious user trying to inspect a freshly downloaded file but running it by accident.
Keeping opening and executing separate actions helps with people protecting themselves from malware, the default handler is an opener, not a runner.
tl;dr of the rest of this: Most open-source programs (whether on accident or on purpose) seem to heed this advice. Some of them don't. Those that don't are quite useful for escaping sandboxes.
Some findings:
Argument injection in sensible-browser (CVE-2017-17512) [1] Argument injection in xdg-open (CVE-2017-18266) [1] Shell command injection in lilypond (CVE-2017-17523, CVE-2018-10992) [1] MIME type spoofing in Firefox/Thunderbird [2] Arbitrary file write in Stellarium file association (CVE-2023-28371) [3] Arbitrary code execution through kitty-open.desktop file association [5]
This type of issue is not uncommon.
[1] https://www.gabriel.urdhr.fr/2018/05/28/browser-injections/ [2] https://www.gabriel.urdhr.fr/2023/03/07/mime-type-spoofing/ Regards,
Gabriel