All addons greyed out / disabled since last upgrade

I just upgraded the firefox package to 62.0~b6+build1-0ubuntu0.18.0 on Ubuntu (bionic), and since then

  1. all my addons are greyed out / disabled,
  2. when attempting to add new ones, Firefox claims that the file was corrupted.

Is this a known issue? Thought I would ask before opening a bug.

I think it’s specific to Ubuntu -

I can’t find a b5 build either so I’ve had to leave the beta channel by downgrading all the way to 61.

sudo apt install firefox=61.0+build3-0ubuntu0.18.04.1

Sometimes downgrading whole versions can cause havoc with user profile data; I’ve not noticed any side-effects like that this time but I am unhappy at such a critical part of the browser being released with no QA testing for anything other than a fully automated nightly channel. Let’s hope they fix it with a new build soon and learn some lessons from the mess.