Well this bites. I just found out that this website, my personal one, had been hacked or attacked and spammers had filled the pages with ads for who knows what. What was interesting is that I couldn’t notice any of this by visiting the site myself. Only after viewing the search results page on Google or Bing or DuckDuckGo did I find it.
Since this is a shared hosting setup, all of the other sites I managed were also hacked, and that’s where the real problems were. The other sites have far more traffic, and thus were bigger targets for the hackers. They were so well broken that in the end I opted to move them to another host and start over (with the core software, not the site) rather than battle with Google over the “Clean or not” state of the site.
All in all, a pretty terrible thing to find out. Hopefully it doesn’t happen again.