[HTTPS-Everywhere] Unsigned extension unable to install in Firefox Nightly

[Some Body]

Hi, I'm trying to install HTTPS Everywhere in Firefox Nightly, however
Firefox won't let me do that, because the extension is unsigned.

I tried to download it from the eff.org site when I got this error, and
I can't find the extension on Mozilla's plugins repo anymore.

Anyone else encountering this issue ?