[GH-ISSUE #4106] [Question] Security advantage of private-tmp for the default firefox profile #2536

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opened 2026-05-05 09:12:43 -06:00 by gitea-mirror · 0 comments

gitea-mirror commented

2026-05-05 09:12:43 -06:00

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Originally created by @BreakfastSerial on GitHub (Mar 17, 2021).
Original GitHub issue: https://github.com/netblue30/firejail/issues/4106

The provided profile for Firefox includes private-tmp. Coming from other discussions (#4103 and #3146), my approach would include multiple active instances of Firefox, with --ignore=private-tmp.

I could not find a reason for the enabled private-tmp option for Firefox. /tmp/ is generally seen as world-writeable, so I don't see much of a security concern with Firefox having access to /tmp/.

However, I do not want to establish a setup with possible security concerns, thus the question:

What was the reason to include private-tmp in the default Firefox profile (/etc/firejail/firefox-common.profile) and what implications would --ignore=private-tmp entail?

Environment

Ubuntu 20.04.2 LTS
Firefox 86.0 (from Ubuntu focal repository)
firejail version 0.9.62

Compile time support:
- AppArmor support is enabled
- AppImage support is enabled
- chroot support is enabled
- file and directory whitelisting support is enabled
- file transfer support is enabled
- firetunnel support is enabled
- networking support is enabled
- overlayfs support is enabled
- private-home support is enabled
- seccomp-bpf support is enabled
- user namespace support is enabled
- X11 sandboxing support is enabled

Originally created by @BreakfastSerial on GitHub (Mar 17, 2021). Original GitHub issue: https://github.com/netblue30/firejail/issues/4106 The provided profile for Firefox includes `private-tmp`. Coming from other discussions ([#4103](https://github.com/netblue30/firejail/issues/4103) and [#3146](https://github.com/netblue30/firejail/issues/3146)), my approach would include multiple active instances of Firefox, with `--ignore=private-tmp`. I could not find a reason for the enabled `private-tmp` option for Firefox. `/tmp/` is generally seen as world-writeable, so I don't see much of a security concern with Firefox having access to `/tmp/`. However, I do not want to establish a setup with possible security concerns, thus the question: What was the reason to include `private-tmp` in the default Firefox profile (`/etc/firejail/firefox-common.profile`) and what implications would `--ignore=private-tmp` entail? **Environment** - Ubuntu 20.04.2 LTS - Firefox 86.0 (from Ubuntu focal repository) - firejail version 0.9.62 Compile time support: - AppArmor support is enabled - AppImage support is enabled - chroot support is enabled - file and directory whitelisting support is enabled - file transfer support is enabled - firetunnel support is enabled - networking support is enabled - overlayfs support is enabled - private-home support is enabled - seccomp-bpf support is enabled - user namespace support is enabled - X11 sandboxing support is enabled

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2026-05-05 09:12:43 -06:00

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2026-05-05 10:19:10 -06:00

[PR #2536] [MERGED] Add fakeroot support for makepkg on Arch #4388

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Reference: github-starred/firejail#2536

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