Comment by ViscountPenguin

That only matters if there's an incentive for LLM a to collaborate with a seperately trained LLM b in order to help the LLM b achieve its goals. So long as you don't let the evaluating LLM tinker with the weights of the evaluated LLM, and as long as you don't believe in very dubious ideas of acausal trade there's no reason to expect this to be an attack vector. For more certainty you can repeat the same analysis with different model classes or approaches aswell.