Wordpress.org have released 2.8.5
It is recommended that all users upgrade as soon as possible.
This is a security release, which hardens some areas of the code, specifically a fairly large fix to prevent a traceback file DOS attack.
Update can be applied from your dashboard as usual. Another interesting link they put on the upgrade post is that there is a useful plugin that allows you to scan your WP Blog for some current known exploits. The plugin is Wordpress Exploit Scanner
Happy upgrading 
