I've been seeing errors in my Apache server log such as:
Call to undefined function site_url() in ... mu-plugins/custom_anti_spam.php on line 264
This apparently occurs on a URL such as:
without any query args.
I noticed that the version of Peter's Custom Anti-Spam plugin is very old. In the Comment Spam Pack it is at version 2.84 from 2007. The latest version is 3.1.4 from Aug 2, 2010:
I checked the latest version and noted that there is no call to site_url().
Can the Comment Spack Pack be updated?