+* 4.x -> 4.4
+
+The syntax of confirmation strings for online registrations has changed and old
+ones no longer work. This only affects users who registered before the upgrade
+but have not yet confirmed their login. You can delete such half-created users
+with 'disorder deluser USERNAME' (as an administrative user, for instance as
+root on the server) and they can start the registration process again.
+
+* 3.0 -> 4.x