local user get created magically ! system hacked ?

[Jehan Procaccia]

hello
I use about a hundred fedora19 stations in computer labs at our school
users accounts comes from an ldap directory and the homedir is 
automounted via NFS.
However, recently I noticed that on some stations, local user account 
had been created !
looking at the log file, I discovered in /var/log/secure  something like 
this:

/accounts-daemon: request by system-bus-name ::1.733 
[/usr/libexec/gnome-initial-setup pid:15259 uid:991]: create user 'foobar'//
//useradd[29724]: new group: name=foobar, GID=1001//
//secure-20131117:Nov 15 17:16:43 b3-4 useradd[29724]: new user: 
name=susana, UID=1001, GID=1001, home=/home/susana, shell=/bin/bash//
//secure-20131117:Nov 15 17:16:43 b3-4 useradd[29724]: add 'susana' to 
group 'wheel'//
//secure-20131117:Nov 15 17:16:43 b3-4 useradd[29724]: add 'susana' to 
shadow group 'wheel'/

Scary ! how comes gnome-initial-setup could create users, and morever 
add them to the wheel group !
could it be a bug in /gnome-initial-setup , /a feature side effect ? or 
our students found a "back door" ?
any suggestion greatly appreciated .

Thanks .

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