There's a pretty serious security bug with WP 1.2.1 (and the current 1.3 alpha), one that can make it so your blog is basically unusable (not permanently, as far as I can tell) but still – if you're using WordPress you should probably make this change.
In any case, here is how you fix the problem. It's a very easy fix. If you can search for text on a page, you can fix this problem.
I hesitated posting this, because I don't want to "start a panic" – nor do I want to give instructions on how to hack WP blogs. But I do think it's important that people go ahead and make this change.
[brought to my attention by Christine]