Before upgrading to WordPress 2.9, WordPress team came out version 2.8.5 a hardening release. Upgrade to WordPress 2.8.5 was a smooth process. No issue so far on 3 of my blogs.
Major fixes on WordPress 2.8.5
- A fix for the Trackback Denial-of-Service attack that is currently being seen.
- Removal of areas within the code where php code in variables was evaluated.
- Switched the file upload functionality to be whitelisted for all users including Admins.
- Retiring of the two importers of Tag data from old plugins.
What are you waiting for? Just use the automatic update to upgrade to WordPress 2.8.5. 🙂