Update the Firefox unsigned extension article to mention the need for a Developer or ESR build of Firefox

[TomasHubelbauer]

Hello! I found your post about installing unsigned extensions to Firefox permanently via Google Search:
https://wiringbits.net/browser-extensions/2020/11/27/installing-unsigned-extensions-permanently-to-firefox.html

I tried the steps myself but could not reproduce the successful end result you describe in your post.

I followed the steps exactly and created my archive file, then selected it in the dropdown in about:addons but I got a UI message telling me the extension was not verified. It had a link which led here:

https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox

On this page it says the following:

What are my options if I want to use an unsigned add-on? (advanced users)
…
Firefox Extended Support Release (ESR), Firefox Developer Edition and Nightly versions of Firefox will allow you to override the setting to enforce the extension signing requirement, by changing the preference xpinstall.signatures.required to false in the Firefox Configuration Editor (about:config page).

This indicates that Firefox Release doesn't allow this setting to change the policy (despite it being there).
I have more support for this information in the answer on this question posted here:
https://discourse.mozilla.org/t/what-is-the-easiest-way-to-install-a-local-unsigned-add-on-permanently/52005

I think either you are missing Firefox Developer (or ESR) and did not mention that in the post or you were using Firefox Release when writing the post in 2020, but since Mozilla locked down this setting to only apply in non-Release builds.

I'm sending in this PR so that you can consider updating the article to mention this.
I knew it was too good to be true when I came across it, but I had to try it just in case.
Unfortunately, Mozilla managed to disappoint so to save future Google Search travelers some time, I am proposing this change so other people know right away they need to succumb to use Firefox Developer or go through the pain of publishing their extensions via AMO (and possibly subject themselves to a cycle of week-long radio silences intertwined with commentless rejections :/).

[TomasHubelbauer]

I have a small update: I tried following the steps in Firefox Developer (already disgruntled as I was not going to keep using Firefox Developer even if it allowed me to use unsigned extensions I wrote myself, but I wanted to be thorough and check everything) and I found that the signature checks need to be turned off and kept off otherwise the unsigned extension won't be enabled to run:

https://github.com/TomasHubelbauer/firefox-permanent-unsigned-extension#update-using-firefox-developer

This means that in the name of security, Firefox forces the user to disable signature checks for all extensions instead of allowing to grant an exception for either a well-known and trusted or even own custom extension. :(

[AlexITC]

Thanks for putting the time to do the research and share these details.

I prepared the guide a few years ago and I while the approach worked, there seem to be many changes since then, I can't even get my Firefox app to accept an unsigned addon.

Back then, I was using Firefox Release version, I followed the approach to install addons in a few computers.

I found that the signature checks need to be turned off and kept off otherwise the unsigned extension won't be enabled to run

This is very unfortunate.

Related to the PR, I have done a few edits and merged manually (see b05d8ec).

Thanks again.