Joomla has released the maintenance version 1.5.18 to correct one priority issue in 1.5.17. You may or may not want to upgrade your Joomla. If you want to upgrade your Joomla, you may always want to see first in Joomla forum if there is any problem caused by the upgrade. You may want to wait for a while until it is sure that there is no critical problem arise after the update. And as always we recommend to always backup first before doing any upgrade.

We have tested to all our templates that the upgrade to Joomla 1.5.18 has no effect to our templates.

Follow this link to know what updates have been added to Joomla 1.5.18:

http://www.joomla.org/announcements/release-news/5276-joomla-1518-released.html