A new version of Firefox is now available. Current users who have autoupdate capabilities will most likely be automatically prompted for updates. More links are noted below:
Product Page
http://www.mozilla.com/firefox/
Release Notes
http://www.mozilla.com/firefox/releases/1.5.0.2.html
Security Enhancements
http://www.mozilla.org/projects/security/known-vulnerabilities.html#firefox1.5.0.2