How to enable Firefox WebExtensions on Mozilla websites

One of the limitations of the new WebExtensions add-on system of the Firefox web browser was up until now that these extensions would not work on some websites operated by Mozilla.

Only WebExtensions are hit by the limitation, and it means that functionality that these extensions provide is not available on sites and services such as addons.mozilla.org or www.mozilla.org.

Extensions cannot manipulate these pages in any way, for instance to provide additional functionality on them, modify content, or even block elements on them.

Mozilla added a new -- hidden -- preference to Firefox 57 that you can set to do away with the limitation in the Firefox web browser.

Hidden preferences are those that are not visible by default when you open the about:config page of the web browser. They do exist, but you do need to know them to set them in the browser.

firefox extensions mozilla unlock

The hidden Firefox preference privacy.resistFingerprinting.block_mozAddonManager removes the WebExtensions restriction.

Here is how you set it:

  1. Load about:config in the Firefox web browser.
  2. You can run a search for privacy.resistFingerprinting.block_mozAddonManager just to make sure it does not exist. It does not in the most recent Firefox Nightly builds at the time of writing.
  3. Right-click in the part of the window that lists the preferences, and select New > Boolean from the context menu.
  4. Name the new Boolean value privacy.resistFingerprinting.block_mozAddonManager.
  5. Set its value to true.

A value of true means that WebExtensions work normally on Mozilla's website. You can undo the change at any time by setting the preference to false on the about:config page of the browser.

Read also:  Block sites on Google Search with Personal Blocklist for Firefox

Mozilla added the new hidden preference to Firefox 57. It is not available in Firefox 56, and there is no option to introduce it in the browser. Firefox Stable users who run WebExtensions right now need to wait until the browser is updated to version 57 to set the preference and gain the functionality

Summary
Article Name
How to enable Firefox WebExtensions on Mozilla websites
Description
Find out how to enable WebExtensions access to mozilla.org websites in the Firefox web browser (Firefox 57 or newer required).
Author
Publisher
Ghacks Technology News
Logo
Advertisement
Please share this article

Facebooktwittergoogle_plusredditlinkedinmail



Responses to How to enable Firefox WebExtensions on Mozilla websites

  1. Pants October 27, 2017 at 12:09 pm #

    FYI: mozAddonManager API only covers these websites - https://dxr.mozilla.org/mozilla-central/source/toolkit/mozapps/extensions/AddonManagerWebAPI.cpp : addons.mozilla.org - discovery.addons.mozilla.org - testpilot.firefox.com

    It was added for the Tor browser uplift. I hope Mozilla do not close this loophole. The protected about pages is not an issue (for me) since I block activity stream etc, and I do not use (and indeed hide) the get addons panel - so this closes all the GA BS'ery once and for all.

    Wish extensions weren't protected :-( Have to pay close attention to what they do and sniff like a beagle now

    • Tony October 27, 2017 at 8:10 pm #

      Do you, any anybody else, understand why this is categorized under 'privacy.resistFingerprinting'?

      • thistyoums October 27, 2017 at 8:24 pm #

        https://bugzilla.mozilla.org/show_bug.cgi?id=1384330

        >In Tor Browser, to protect against fingerprinting, we block window.navigator.mozAddonManager data from being exposed to AMO. We would like to propose uplifting this protection behind the "privacy.resistFingerprinting" pref.

      • Pants October 27, 2017 at 11:55 pm #

        Because it stops data being exposed to AMO (which can lead to tracking, FP'ing etc). Tor have no interest in AMO, they just want all users and data treated the same: i.e anonymous and protected as much as possible

        https://bugzilla.mozilla.org/show_bug.cgi?id=1384330

      • Chris October 28, 2017 at 8:19 am #

        So, wait, it's concern that info is being exposed to AMO?

        If you're okay with data being exposed to AMO (and only AMO) is there any harm in enabling this pref?

      • Anonymous October 28, 2017 at 10:12 am #

        AMO respects Do Not Track. If you go there with DNT enabled you don't need to have anti-fingerprinting measures on Mozilla sites.

        I tend not to use DNT, so I am happy that this pref is implemented into Firefox 57. To be honest I didn't believe there wouldn't be such a pref by at least 58.

      • Anonymous October 28, 2017 at 10:12 am #

        *by 58 at the latest

    • Anonymous October 28, 2017 at 10:15 am #

      > Wish extensions weren't protected :-( Have to pay close attention to what they do and sniff like a beagle now

      Aren't special rights being discussed ? I think I saw something like that, where for instance uBO would be able to control another add-on.

      When I read that on Bugzilla, I couldn't be certain that my understanding was correct. On top of that it was a couple months ago and my memory could be failing me. But I've got some vague hope lingering since then.

  2. happysurf October 27, 2017 at 2:10 pm #

    Absolutely fantastic tip.
    Thank you Martin.

  3. thistyoums October 27, 2017 at 6:12 pm #

    For those who care about security implications https://bugzilla.mozilla.org/show_bug.cgi?id=1406795

    • Chris October 28, 2017 at 8:21 am #

      Read it. Confused. Outside of a rogue extension modifying AMO, is there any risk?

      • Anonymous October 28, 2017 at 10:09 am #

        From what I understand, as long as you read UI prompts properly, you're safe even if a rogue extension that you installed modifies AMO. But if you have a rogue extension you really have other problems than having it trick you into installing another rogue extension.

  4. Nicolas October 30, 2017 at 5:30 pm #

    Great! It also works for Firefox Screenshots.

  5. amb November 6, 2017 at 11:39 am #

    Is there a pref. like this to make extensions work on internal pages, like about:addons and about:newtab?

Leave a Reply