diff -Nru lightdm-1.22.0/debian/50-disable-guest.conf lightdm-1.22.0/debian/50-disable-guest.conf
--- lightdm-1.22.0/debian/50-disable-guest.conf	1970-01-01 12:00:00.000000000 +1200
+++ lightdm-1.22.0/debian/50-disable-guest.conf	2017-05-09 09:32:16.000000000 +1200
@@ -0,0 +1,4 @@
+# Disable guest sessions due to them not being confined in systemd
+# https://bugs.launchpad.net/bugs/1663157
+[Seat:*]
+allow-guest=false
diff -Nru lightdm-1.22.0/debian/changelog lightdm-1.22.0/debian/changelog
--- lightdm-1.22.0/debian/changelog	2017-04-05 10:34:32.000000000 +1200
+++ lightdm-1.22.0/debian/changelog	2017-05-09 09:32:16.000000000 +1200
@@ -1,3 +1,13 @@
+lightdm (1.22.0-0ubuntu2.1) zesty-security; urgency=medium
+
+  * SECURITY UPDATE: Guest session not confined (LP: #1663157)
+    - debian/50-disable-guest.conf:
+    - debian/lightdm.install:
+      - Disable guest sessions by default, this can be overridden by custom
+        configuration (e.g. /etc/lightdm/lightdm.conf)
+
+ -- Robert Ancell <robert.ancell@canonical.com>  Tue, 09 May 2017 09:32:16 +1200
+
 lightdm (1.22.0-0ubuntu2) zesty; urgency=medium
 
   * SECURITY UPDATE: Directory traversal allowing arbitrary directory
diff -Nru lightdm-1.22.0/debian/lightdm.install lightdm-1.22.0/debian/lightdm.install
--- lightdm-1.22.0/debian/lightdm.install	2017-04-05 09:25:43.000000000 +1200
+++ lightdm-1.22.0/debian/lightdm.install	2017-05-09 09:32:16.000000000 +1200
@@ -19,3 +19,4 @@
 debian/50-greeter-wrapper.conf usr/share/lightdm/lightdm.conf.d
 debian/50-guest-wrapper.conf usr/share/lightdm/lightdm.conf.d
 debian/50-disable-log-backup.conf usr/share/lightdm/lightdm.conf.d
+debian/50-disable-guest.conf usr/share/lightdm/lightdm.conf.d