[, simply update your httpd.conf with the following rules:
<IfModule mod_security.c> SecFilterEngine On SecFilterDefaultAction "deny,log,status:412"
`# RULES: Prevent Wordpress 2.1.1 attack
http://wordpress.org/development/2007/03/upgrade-212/
SecFilter “ix=” SecFilter “iz="`
[...]
</IfModule>
And then restart Apache. Note that while this is an effective temporary workaround, upgrading is recommended. Also, any install other than 2.1.1 is not effected.