Hi everyone :)

For those interested, I share my just finished personal Firefox user.js. It’s based on the latest arkenfox and has the same privacy features, with some personal tweaks to fit my workflow. And also easier to read 😅.

https://github.com/KalyaSc/fictional-sniffle/blob/main/user.js

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KEEP IN MIND

Except for the privacy focused entries, some are personal choices for an easy drop-in Firefox preferences backup. This is what I consider a good privacy model and some entries could break YOUR workflow, especially if you don’t have self-hosted alternatives (Vaultwarden, Linkding, Wallabag).

I’m not an expert, but most of those entries are the same as Arkenfox’s user.js. I really encourage you to read their file for better understanding on what each entrie does. While my file is easier to read, one downside is the lack of documentation for each entries.

Also, this is not just a COPY/PAST. It took a lot of effort, time, reading, testing and understanding. I kept a similar naming scheme for cross referencing.

I learned a few things and hope that you also will enjoy, edit, read and learn new interesting things.

Happy hardening !

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Features

• Automatic dark mode theme (Keep in mind you still need Dark Reader or similar plugin for web pages in dark mode.)
• Deep clean history on every Firefox quit. Only cookies as exception are kept. I need them for my self hosted services.
• Disable password/auto-fill/breache. Vaultwarden takes care of everything.
• All telemetry disabled by default except for the crash reports. To also disable the crash reports, comment the begining of the following lines with //:

user_pref("breakpad.reportURL", "");
user_pref("browser.tabs.crashReporting.sendReport", false);
user_pref("browser.crashReports.unsubmittedCheck.enabled", false);
user_pref("browser.crashReports.unsubmittedCheck.autoSubmit2", false);

• DoH disabled (got my personal VPN with DoH enabled)

user_pref("network.trr.mode", 5);

• Disable WebRTC. If you need it for video calling, meetings, video chats:

Comment the following line:

user_pref("media.peerconnection.enabled", false);

Uncomment the following (arkenfox default, it will force WebRTC inside your configured proxy)

//user_pref("media.peerconnection.ice.default_address_only", true);
//user_pref("media.peerconnection.ice.proxy_only_if_behind_proxy", true);

• FIxed Width and Height (1600x900) (Finger print resistant) arkenfox’s default
• Resist Fingerprinting (RFP) which overrides finger print protection (FPP)
• Alot of other tweaks you can discover while reading through the file.

How to use/test this file ?

Open firefox, type about:profiles and create a test profile. Open the corresponding root folder, put in the user.js and launch profile in a new browser.

After testing and happy with the result, BACKUP your main Firefox profile somewhere safe and put the user.js in your main profile to see if it fits your workflow.

Room for improvement / TODO.

Alot of the settings in the 5000 range form arkenfox’s user.js need further testing and investigation, because they could breake and cause performance/stability issues.

• JS exploits:

- javascript.options.baselinejit
- javascript.options.ion
- javascript.options.wasm
- javascript.options.asmjs

• Disable webAssembly
• …

TODO

• Disable non-modern cipher suites
• Control TLS versions
• Disable SSL session IDs [FF36+]

Also those settings are another beast that needs further testing/investigation on how they work.

The user.js file

https://github.com/KalyaSc/fictional-sniffle/blob/main/user.js

WARNING

Arkenfox advise agianst addons who scramble and randomize your fingerprint characteristics (like chameleon).

WHY? Because resist fingerprint takes care of most things. See 4500: RFP (resistFingerprinting) in arkenfox user.js.

[WARNING] DO NOT USE extensions to alter RFP protected metrics

    418986 - limit window.screen & CSS media queries (FF41)
   1281949 - spoof screen orientation (FF50)
   1330890 - spoof timezone as UTC0 (FF55)
   1360039 - spoof navigator.hardwareConcurrency as 2 (FF55)
 FF56
   1333651 - spoof User Agent & Navigator API
      version: android version spoofed as ESR (FF119 or lower)
      OS: JS spoofed as Windows 10, OS 10.15, Android 10, or Linux | HTTP Headers spoofed as Windows or Android
   1369319 - disable device sensor API
   1369357 - disable site specific zoom
   1337161 - hide gamepads from content
....

Very long list !

Final words

I’m open for any constructive criticism or any constructive comment that could help me out to improve or understand something new or something I misunderstood. Sure that’s not 100% my work, but as I said it took a lot of time, testing, searching, reading… Please don’t be a crazy Panda…

Credits

https://github.com/arkenfox/user.js

https://github.com/pyllyukko/user.js/

https://wiki.archlinux.org/title/Firefox/Privacy