There is an important anti-spam update to MovableType. It closes a hole in the mail sending program that presently allows spammers to send unlimited e-mails through your installation.
You can download the complete MT program or just a plug-in. I'm getting the plug-in as I'm getting real tired of having to do complete re-installs every time MT makes a change to one file. But I digress as this is not the time to talk about MT's user unfriendly installations.
Anyway, if you are using MT, please get the update as soon as possible.