I have to disagree a bit about the the duplicates here. This very old bug was when Firefox was using GTK2, and back then the scroll bars in Firefox were GTK2-standard and didn't use the overlay scrollbars (up and down buttons).
All the newer bugs have GTK3 Firefox, and that the scroll bar in Firefox is thin and does not expand, or is not thick by default as in Adwaita. In Adwaita, the scroll bar is already thick and easily handled. ** This bug is no longer a duplicate of bug 767040 Firefox doesn't use overlay scrollbars ** Changed in: ubuntu-themes (Ubuntu) Status: Invalid => New -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to firefox in Ubuntu. https://bugs.launchpad.net/bugs/1762551 Title: Scroll bar in Firefox is very thin and does not widen when hovered Status in firefox package in Ubuntu: Confirmed Status in ubuntu-themes package in Ubuntu: New Bug description: In Ambiance, the scroll bar in Firefox is very thin and does not widen when hovered or pressed. In Adwaita, the scroll bar is thicker and easier to see and pressed. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: light-themes 16.10+18.04.20180328-0ubuntu1 ProcVersionSignature: Ubuntu 4.15.0-13.14-generic 4.15.10 Uname: Linux 4.15.0-13-generic x86_64 ApportVersion: 2.20.9-0ubuntu4 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Mon Apr 9 22:56:52 2018 InstallationDate: Installed on 2017-10-02 (189 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Beta amd64 (20170930) PackageArchitecture: all SourcePackage: ubuntu-themes UpgradeStatus: Upgraded to bionic on 2018-03-27 (13 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1762551/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : email@example.com Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp