WordPress versions between 2.8.0 and 2.8.3 have a major security issue which allows anyone (not just hackers, but literally anyone) to change the admin password on your blog in a matter of minutes. Full info can be found here. Version 2.8.4 was created to remedy that and I hope most of you already upgraded. Many people will not click the upgrade link right away and even more will not bother to read the explanation on the development blog about the latest patch.