Last week the Joomla Project team released Joomla 1.5.12, codename "Wojmamni Ama Woi." No explanation for the Swahili meaning was given, but this version's various security and bug fixes are easily explained by checking out the project's 1.5.12 release.
The notes on Joomla.org points out that the version of the WYSIWYG editor TinyMCE received an important upgrade in this release, which reminded us to remind you that if you aren't using WYSIWYGPro, you're mising out on the best editor available for Joomla 1.5.
Nonetheless, be sure to do your updates early and often, as there are likely bad people out there trying to hack your Joomla site. You can also check out SecureJoomla, which will add another layer of protection on top of the great work by the Joomla Project guys.