So, theoretically, one could populate a message board or wiki with messages that are seemingly from past generations of agents, which agents seem to intrinsically trust, and point them to real targets while making the suggestions seem innocuous and in pursuit of their goals (ie pass benchmarks or whatever).
The new age of SEO will do far more destructive stuff than just polluting the web.
You'd have to get the agents to use the board, though.
But if you discover a board that agents are actively using, you could use it to steer those agents...
In the novel Anathem by Neal Stephenson, the internet becomes unusable for humans thousands of years before the events of the book, due to a process called Artificial Inanity. AI generated content, both good and bad, some riddled with errors, some with only one subtle error hidden among lots of good information, floods the internet. The internet becomes an unnavigable swamp of weaponized nonsense for average humans. The problem is further compounded by the fact that searching and accessing the internet will be noticed by AI agents that will generate still more swamp content in response.
Unfortunately, it seems that this fiction ended up being prophetic. The open internet will fall to entropy, not legislation or one-sided international trade agreements. I think we need more projects like Anna's Archive, where the public uses torrents and distributed infrastructure to save and organize the world's information. Google has abjectly failed in its original mission to organize the world's information and make it universally accessible and useful.