Is Google serving up ads targeted at sites which categorize themselves as “extreme porn,” bestiality,” and “child porn”? Rest assured, it is not. But if you are a website publisher using DoubleClick’s Ad Planner to select categories to match your site to advertiser’s interests, you might think so. The screenshot at right and below shows what one publisher found when choosing self-descriptive categories. Under “Adult” and “Porn” are those three categories. The issue was first brought to Google’s attention in this help forum, and subsequently by TechCrunch.

It turns out this is a software bug, but what a doozy. DoubleClick, which is part of Google, maintains a blacklist of categories and keywords it will not serve ads against. Those include “extreme porn,” “bestiality,” and “child porn.” Somehow categories from the blacklist started appearing as regular options within Ad Planner. Google is removing those now and says no ads were actually served against those categories even if somebody selected them.

A Google spokesperson provided us with the following statement:

“This was a mistake that we are fixing. This screenshot is from the Ad Planner Publisher Center, where we allow publishers to claim their sites and self-identify the categories of content that their sites showcase. We maintain an internal list of categories of policy-violating content to prevent that content from entering the network, and due to an error some items from that list were recently surfaced in the Publisher Center UI. We are working to correct this error immediately, and we can confirm that it was strictly an error in the publisher interface. No advertiser has ever had or will ever have the ability to target ads to categories like child pornography or bestiality.”

That’s reassuring. But how does a mistake like that happen in the first place?