Pressing the control key causes the font size to increase

[j1n3l0]

Since updating to the current version of firefox any time I touch the
Control key (either left or right) on several keyboards (thus far I
have tried 3 including a bluetooth and mac keyboard), the font size
starts increasing up to the maximum allowed on the site.

This problem appears to be limited to firefox.

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: firefox 56.0+build6-0ubuntu0.17.04.2
ProcVersionSignature: Ubuntu 4.10.0-35.39-generic 4.10.17
Uname: Linux 4.10.0-35-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.20.4-0ubuntu4.5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: nelo 2197 F.... pulseaudio
 /dev/snd/controlC1: nelo 2197 F.... pulseaudio
BuildID: 20171003100843
Channel: Unavailable
CurrentDesktop: GNOME
Date: Thu Oct 5 10:29:49 2017
Extensions: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
InstallationDate: Installed on 2017-06-30 (96 days ago)
InstallationMedia: Ubuntu-GNOME 17.04 "Zesty Zapus" - Release amd64 (20170412)
Locales: extensions.sqlite corrupt or missing
PrefSources:
 /usr/lib/firefox/defaults/pref/all-ubuntu-gnome.js
 prefs.js
ProcEnviron:
 LANGUAGE=en_GB:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
Profiles: Profile0 (Default) - LastVersion=56.0/20171003100843 (In use)
RunningIncompatibleAddons: False
SourcePackage: firefox
Themes: extensions.sqlite corrupt or missing
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/12/2015
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: M71 Ver. 01.08
dmi.board.name: 225A
dmi.board.vendor: Hewlett-Packard
dmi.board.version: KBC Version 96.55
dmi.chassis.asset.tag: 5CG5402RWH
dmi.chassis.type: 10
dmi.chassis.vendor: Hewlett-Packard
dmi.modalias: dmi:bvnHewlett-Packard:bvrM71Ver.01.08:bd08/12/2015:svnHewlett-Packard:pnHPEliteBook820G2:pvrA3009D510303:rvnHewlett-Packard:rn225A:rvrKBCVersion96.55:cvnHewlett-Packard:ct10:cvr:
dmi.product.name: HP EliteBook 820 G2
dmi.product.version: A3009D510303
dmi.sys.vendor: Hewlett-Packard

[dino99 (9d9)]

That version is now dead
http://news.softpedia.com/news/ubuntu-17-04-zesty-zapus-has-reached-end-of-life-upgrade-to-ubuntu-17-10-now-519360.shtml