The cause of this bug is the unity-menubar.patch file, which Ubuntu and various other distros use to integrate firefox's menubar with Unity's, was updated but the context around that patch changed (ie Firefox changed) and the patch did not take that into account.
https://github.com/archlinuxcn/repo/blob/master/firefox-kde-opensuse /unity-menubar.patch#L5381 shows that the patch is trying to run the 'filter' method on `toolbarNodes`, but as of 59, `toolbarNodes` is no longer an array, it's just a list of child nodes, and so it has no `filter` method, and the call throws an exception. To get this fixed someone needs to update that patch to enforce that it's using an array. (sorry for the arch link, pretty sure Ubuntu is using the same debian patch, but I just spent 15 minutes trying to find a source link (online vcs rather than, say, a tarball which I obviously can't link into) that's used for ubuntu's package and can't, so...) ** Bug watch added: Mozilla Bugzilla #1428938 https://bugzilla.mozilla.org/show_bug.cgi?id=1428938 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1758107 Title: Firefox: View > Toolbars is Missing "Bookmarks Toolbar" To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/firefox/+bug/1758107/+subscriptions -- ubuntu-bugs mailing list firstname.lastname@example.org https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs