You might have come across the security bulletin already, but there's quite a serious security issue in the PHP XML-RPC Library that is used by Nucleus and a bunch of other projects. Untill we have a new package available for download with the updated library, here is how to disable XML-RPC support on Nucleus

Weiterlesen bei nucleuscms.org

Update: Das Problem ist mit Nucleus 3.21 behoben.

Aehnlich scheint das Problem bei WordPress zu sein, aber da gibts bereits ein Update:

The problem is not yet public but you should update your blog as soon as possible to 1.5.1.3. If you are unable to do upgrade in the short-term you may protect yourself by deleting the xmlrpc.php file from your WordPress directory.

Andere Blogsysteme duerften ebenso betroffen sein.