doesn't do anything : firefox gets no module added

[Otyugh]

The title say everything. Nothing is installed as module in firefox after the package is installed.
Tested from clean install. I also had the same issue with xul-ext-https-finder.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xul-ext-ublock-origin 1.13.8+dfsg-1
ProcVersionSignature: Ubuntu 4.15.0-33.36-generic 4.15.18
Uname: Linux 4.15.0-33-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Aug 28 04:11:47 2018
InstallationDate: Installed on 2018-08-28 (0 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: ublock-origin
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.