[Digital Jedi]

I'm not sure who they are or their motivation (it's a forum about parrots, hardly controversial).

They don't need any. Seldom is it a personal attack. They just see a site, see a vulnerability and abuse it...because they can. Hacking is usually out of the most childish of motivations. The same thing that makes a bully pick on smaller kids in school.

I don't think any of those mods have security vulnerabilities, as quite a large number of sites use them. Make sure all of your sites folders are protected by an index file. Changing your administrators passwords was a good idea as well, in case one of them was compromised.