Installing firefox extension for all users [system wide installation]

Question

I have written a Firefox extension which is packed as an .xpi file. I want to install this extension for all users. Somewhere I found that we can achieve this by putting the file in the Mozilla\Extensions folder, then the extension will be available to all users.

But the problem is after installing the extension, on first launch of Firefox

• for an administrator, a pop-up tab will appear to ask whether to enable or disable the extension, but
• for the non-admin user, no pop-up will be there and the extension will be disabled for them initially.

Is it possible to notify every user by launching a pop-up tab when they start the browser the first time after installation?

Answer 1

Just to provide the old answer, which no longer worked flawlessly:

If you want to do a silent administrative install [...]:

uncompress the .xpi file yourself (as a ZIP file) to an appropriately named (extension's ID) folder. On Linux/Unix platforms you can use a helper script to determine extension IDs in an automated fashion.

Put this directory into the browser/extension folder.

See also this answer about Thunderbird (by me). The same steps worked for Firefox before application signing was enforced. In Firefox 43, the signature checks can be disabled via about:config. The about:config workaround will supposedly stop working in Firefox 44.