Moving my blog to the WordPress platform, I wanted to install a template somewhat nicer than the default. This is how I discovered a potentially very harmful stunt which some blackhats are pulling in free WordPress templates. What they do is build sort of “template farms” where they keep a directory of hundreds or maybe thousands of templates. As these sites are very well optimized for search engines, they rank pretty high when the unsuspecting victim is looking for some free templates. Sometimes, the victim just downloads a nice-looking template from a seemingly inocuous blog hosted on a free platform (wordpress.com,blogger,etc.).
Do not install a WordPress template without performing at least a cursory security audit. Let me remind you that the view layer in WordPress is just another PHP script with full power to do anything a PHP script can do on your server. This is what the template I’ve downloaded contained embedded in multiple source files (sidebar, archive, etc.):
Basically, this means that any UserAgent containing the word “bot” (thus, all the mainstream search engine bots/site crawlers) will see a couple of spammy links on all the pages of the blog. Obviously it could have been much worse, as one can reveal the database access coordinates and other server-related dangerous things when a blackhat bot identified by a specially crafted UserAgent text is scanning the blog. The simplest form of audit one can do is to search for base64 and eval functions in the PHP source code as these are generally used to disguise malware.