WordPress 3.0.5 & 3.1 RC4  has been released:
WordPress 3.0.5  is now available and is a security hardening update for all previous WordPress versions.
This security release  is required if you have any untrusted user accounts, but it also comes with important security enhancements and hardening. All WordPress users are strongly encouraged to update.
Three point oh point five
Three point one comes soon
The release addresses a number of issues and provides two additional enhancements:
Two moderate security issues were fixed that could have allowed a Contributor- or Author-level user to gain further access to the site.
One information disclosure issue was addressed that could have allowed an Author-level user to view contents of posts they should not be able to see, such as draft or private posts.
Two security enhancements were added. One improved the security of any plugins which were not properly leveraging our security API. The other offers additional defense in depth against a vulnerability that was fixed in previous release.
Thanks to Nils Jueneman and Saddy for their private and responsible disclosures to email@example.com for two of the issues. The others were reported or repaired by our security team.
WordPress 3.1 RC4
The Release Candidate 4 build includes the security fixes and enhancements included in 3.0.5 and addresses about two dozen additional bugs. This includes fixes for:
- Deleting a user and reassigning their posts to another user.
- Marking multiple users or sites as spam in multisite.
- PHP4 compatibility.
- Post it to the Alpha/Beta area in the support forums 
- Report it to the wp-testers mailing list 
- Join the development IRC channel and tell us live at irc.freenode.net #wordpress-dev
- File a bug ticket on the WordPress Trac 
To test WordPress 3.1, try the WordPress Beta Tester plugin  (you’ll want “bleeding edge nightlies”). Or you can download the release candidate here  (zip). If any new issues become known, you’ll be able to find them here .
After nearly five months of development and testing, we think we’re very close to a final release. Users and developers, please test your themes and plugins.
Download: WordPress 3.1 RC4