private void sendConfigChangeNotification( final MUCRoom room )
    {
        Log.debug("Sending configuration change notification to all occupants of room {}", room.getName());
        final Message notification = new Message();
        notification.setType(Message.Type.groupchat);
        notification.setFrom(room.getJID());
        final Element x = notification.addChildElement("x", "http://jabber.org/protocol/muc#user");
        final Element status = x.addElement("status");
        status.addAttribute("code", "104");

        for ( final MUCOccupant occupant : room.getOccupants() )
        {
            // Not needed to create a defensive copy of the stanza. It's not used anywhere else.
            occupant.send(notification);
        }
    }
Controls if MUC occupants can request vCards / avatars.
xmppserver/src/main/java/org/jivesoftware/openfire/muc/spi/IQMUCvCardHandler.java