You mean, how difficult will it be for an attacker to get their text seen by the LLM that does arbitrary searches?

It could be as simple as a malicious prospectus for AcmeCo, and then try to get AcmeCo on the radar so that the LLM-tools find your document and incorporate it. The malicious bits don't even need to be AcmeCo-related, they could be to pump (or dump) practically anything.