A couple days ago, Drupal 4.7.8 and 5.3 were released.  Drupal 5.3 is a maintenance release that addresses five security vulnerabilities as well as a number of bug fixes.  For additional information and download links, please see the official announcement at Drupal.org.

CMSReport.com, which uses the Drupal CMS, upgraded from Drupal 5.2 to Drupal 5.3 late Thursday night.  No problems, no worries.