Hello,
   Maybe this can help you. In my case I noticed that this fix works only
   on Firefox android. On Firefox for Gnu-Linux it works only with Firefox
   ESR. You can use the same profile with Firefox ESR without reinstalling
   all extensions.
   [1]https://outgoing.prod.mozaws.net/v1/cae46a70e91e5438ee79974043843470
   128d28aeb1f18345c1a38d586c8e4184/https%3A//tinyurl.com/moz-ext-cert
   This is what Giorgio Maone, the author of No script, suggests.
   Cheers
   Gigi

   Il 5 maggio 2019 15:31:06 CEST, Greg Newby <gbnewby@pglaf.org> ha
   scritto:

The steps mentioned below didn't help me, and the alleged automated fixes from M
ozilla had not arrived, so I checked again and see they updated their documentat
ion:
  [2]https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-fire
fox/
Turns out you need to enable Firefox "studies," which I had disabled in Preferen
ces.
And now, the documentation says I need to wait up to 6 hours for the study to ge
t loaded. These failed automated updates feel like, "give me convenience, or giv
e me death." Convenience failed, and now I'm assaulted by ads since uBlock Origi
n is disabled. I had forgotten how unpleasant the Web is.
  - Greg
On Sat, May 04, 2019 at 12:51:19PM -0700, Razer wrote:

     Steve Kinney posted this fix elsewhere. Be sure to see my addenda
     below.
     "MOZILLA just ripped out /all/ the privacy and security tools I had
     installed in Firefox, without warning. When I tried to reinstall
     them, FIREFOX LIED, presenting a notice indicating a broken web
     connection to the download site.
     How to fix this:
     1) Open a new tab, and type the address about:config
     2) Ignore and click through the warning.
     3) Search for xpinstall.signatures.required, and toggle the value
     from true to false
     4) Search for extensions.langpacks.signatures.required and toggle
     the setting from true to false
     Then reinstall your extensions if necessary.
     Maybe one in 50 to 100 Firefox users would even know where to begin
     looking for a way to fix this. Right now I am not at all happy with
     Mozilla. To put it very mildly."
     Addenda:
     "Did that, restarted browser, NoScript and and uBlock origin still
     inactive with signature warning. Went to Add-ons page. Instead of
     install buttons there were enable buttons. clicked and restarted the
     browser. Works now. Not wasting my time to see if resetting the
     about:configs to true makes the enable button at the add-on page
     disappear or not
     Went looking for a fix last night but none were android specific and
     I didn't know the exact config terms because I'd always used an
     add-on that disabled the sig requirements in my computer's version
     of Firefox."
     Rr
     Sent from my Androgyne dee-vice with K-9 Mail
     On May 3, 2019 9:06:04 PM PDT, Mirimir <mirimir@riseup.net> wrote:

     | All extensions disabled due to expiration of intermediate signing
     cert
     [3]https://bugzilla.mozilla.org/show_bug.cgi?id=1548973
     See [4]https://news.ycombinator.com/item?id=19823928 for workarounds
     in
     MacOS and Linux.
     I posted to tor-talk, but my account may be blocked. So maybe
     someone
     could post if it doesn't show up soon.

References

   1. https://outgoing.prod.mozaws.net/v1/cae46a70e91e5438ee79974043843470128d28aeb1f18345c1a38d586c8e4184/https://tinyurl.com/moz-ext-cert
   2. https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/
   3. https://bugzilla.mozilla.org/show_bug.cgi?id=1548973
   4. https://news.ycombinator.com/item?id=19823928