We wanted to start out this article by giving you tips for securing Movable Type, but there were not many resources online that cover this. We recommend checking their official Security page periodically for updates, it can be viewed here:
Generally, we recommend using strong passwords and always running the latest version of Movable Type, and any CMS. The company that produces Movable Type (Six Apart Ltd.) stops updating a version after 2.5 years from the release date, so it is highly recommended to keep your Movable Type installation up-to-date. At the time this was written, the latest version of Movable Type was 5.2.3
Here is a list of Movable type version and the date they will no longer be updated as per movabletype.org
will be discontinued.
If you are running any of these versions after the date listed, it is highly recommended that you perform an update. This is to avoid getting your Movable Type website compromised.