Zikula Core 1.3.9 is released as of 22 August 2014. This is a security release for the Core 1.3.x series. All users of Core 1.3.0 - 1.3.8 are recommended to update as soon as possible.
Installation/Upgrade: Be sure to backup files and database before any upgrade is attempted. Simply overwrite the files in your current installation with the new files , add your DB credentials to the config.php file and run the upgrade.php routine.
A full Changelog is available.