The extension is disabled because it isn't signed

[Luca Olivetti]

This package (or better said its binary xul-ext-kwallet5) doesn't work with firefox 46.0.1.
It says "this add-on could not be verified for use in Firefox and has been disabled".
See https://support.mozilla.org/en-US/kb/add-on-signing-in-firefox
Setting xpinstall.signatures.required to false works around the problem but I'm not comfortable using that setting.

$ lsb_release -rd
Description: Ubuntu 16.04 LTS
Release: 16.04

$ apt-cache policy xul-ext-kwallet5
xul-ext-kwallet5:
  Instaŀlat: 1.0-1
  Candidat: 1.0-1
  Taula de versió:
 *** 1.0-1 500
        500 http://es.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
        100 /var/lib/dpkg/status

[Luca Olivetti (olivluca)]

I forgot to specify the version of firefox

$ apt-cache policy firefox
firefox:
  Instaŀlat: 46.0.1+build1-0ubuntu0.16.04.2
  Candidat: 46.0.1+build1-0ubuntu0.16.04.2
  Taula de versió:
 *** 46.0.1+build1-0ubuntu0.16.04.2 500
        500 http://es.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
        100 /var/lib/dpkg/status
     45.0.2+build1-0ubuntu1 500
        500 http://es.archive.ubuntu.com/ubuntu xenial/main amd64 Packages