Disable add-on signature enforcement in Firefox 49 and above

Starting with Firefox 48, Mozilla made the add-on signature enforcement mandatory. The user cannot disable it using the about:config flag or using any other method. Here is a hack which will allow you to bypass the requirement and install unsigned addons in the browser.


While Firefox now comes without the option to use unsigned addons, there are a number of ways to bypass the add-on signature requirement. One of them involves a system script that defines which browser objects should request the digital signature. If you modify the script, it will be possible to install add-ons. Follow the instructions below.

Disable add-on signature enforcement in Firefox 49 and above

  1. Open Notepad and paste the following text:
    //
       try {
       Components.utils.import("resource://gre/modules/addons/XPIProvider.jsm", {})
       .eval("SIGNED_TYPES.clear()");
       }
       catch(ex) {}

    firefox-create-config-js

  2. Save your file under the name "config.js". I suggest you to include the file name in quotes in Notepad's Save dialog as shown in the screenshot below. Otherwise, Notepad may append a ".txt" extension to the file name, making it "config.js.txt".
    firefox-save-config-js
  3. Now, copy or move the config.js file you created to the following location.
    In Linux 32-bit:

    /usr/lib/firefox-VERSION

    In Linux 64-bit:

    /usr/lib64/firefox-VERSION

    In Windows 32-bit:

    C:\Program Files\Mozilla Firefox

    In Windows 64-bit

    C:\Program Files (x86)\Mozilla Firefox

    firefox-copy-config-js

    firefox-copy-config-js-2

  4. Create a new text file again in Notepad with the following content:
    pref("general.config.obscure_value", 0);
    pref("general.config.filename", "config.js");

    firefox-create-config-prefs-js

  5. Save the text above to a file named config-prefs.js. firefox-save-config-prefs-js
  6. Run Firefox and open Help -> Troubleshooting Information. The following page will be opened: firefox-open-help-troubleshooting firefox-troubleshooting-page
  7. Scroll down to the line "Profile folder" and click the "Show folder" button on the right. The folder will be opened in File Explorer. firefox-opened-profile-folder
  8. Copy or move the config-prefs.js file you have created to this folder: firefox-put-config-prefs-js-in-the-profile
  9. Restart Firefox.
  10. If it does not work, try to put the file config-prefs.js in the folder
    C:\Program Files\Mozilla Firefox\defaults\pref

    Then restart the browser. Thanks to our reader Macgryver for this tip.

That's it. After you put the required files to the locations mentioned above, Firefox won't require digital signatures for add-ons. The first script is a configuration file which clears the SIGNED_TYPES array, which points the browser to identify add-ons as objects that require signing. The second file activates the first script.
To undo the changes you made, just delete these two files and restart the browser. Thanks to OpenNews for sharing this tip.

9 thoughts on “Disable add-on signature enforcement in Firefox 49 and above

  1. Thorn Hart

    Thanks! This is great! I was hoping for a solution to this! :D

    Like or Dislike: Thumb up 1 Thumb down 0

    Reply
  2. Alex

    Very sorry, but on Mozilla Firefox 49.0.1 it didn’t work… At least to install uBlock Origin RC1 either through the browser or via installation from a file by specifying the directory of the downloaded file…

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  3. Zac

    Make sure xpinstall.signatures.required is set to false in about:config to allow unverified add-ons to be enabled.

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    1. Sergey Tkachenko Post author

      Correct me if I am wrong, but that preference was already removed?

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      1. Zac

        Initially after following the above instructions, it did NOT work. Then I toggle xpinstall.signatures.required
        then restart and toggle it again then restart … and suddenly it works.

        Today when I started firefox (Linux Mint), I noticed that it did NOT work again.

        Maybe somebody knows an alternative solution. Thanks.

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  4. Macgryver

    using ff50.0…not working…I have installed firefox on custom location…will I have to change anything?
    thanks

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  5. Macgryver

    Here’s a solution…
    You to put the file config-prefs.js to
    C:\Program Files\Mozilla Firefox\defaults\pref or
    C:\Program Files (x86)\Mozilla Firefox\defaults\pref
    or for custom installation directory\defaults\pref
    Thanks

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    1. Sergey Tkachenko Post author

      It should be placed in the profile dir.

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  6. Paul

    I’t didnt work on any configuration suggested. I should stick to FF 46, the last version that after tweaking allowed my old friend extentions to work

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