Novel Claim or Déjà Vu? Rethinking "Contamination-Free'' Dynamic Evaluation for Multimodal Automated Fact-Checking
This paper challenges the assumption that dynamic benchmarks are inherently contamination-free by demonstrating that a significant portion of post-cut-off claims remain verifiable via pre-existing knowledge, which can artificially inflate multimodal fact-checking performance and distort system rankings, thereby necessitating stricter evaluation protocols.