One of the reasons I moved away from Wordpress was the fact that I seemed to be permanently backdoored with shady content showing up to search engines but not to normal users. Moving to a static site was not a bad idea after all, after seeing this recent report on ArsTechnica that hundreds of Wordpress site were backdoored. It is likely true that this is not a problem with Wordpress per se, but with addons that have vulnerabilities, including those that have been abandoned but still in use. If you do decide to use Wordpress, you have to absorb that risk or face the consequences.