When the Model Knows but Doesn't Remember: The Hidden Blind Spot in LLM Contamination Detection
Audit. That is the word companies like to use when they want uncertainty to sound disciplined. Model audit. Benchmark audit. Contamination audit. The phrase suggests a clean checklist: run the detector, read the score, decide whether the benchmark is safe. The paper behind today’s article makes that picture less comfortable. It studies Contamination Detection via output Distribution, or CDD, on small language models and finds a simple but awkward failure mode: a model can be trained on contaminated benchmark examples, learn from them, and still avoid the kind of verbatim memorization that CDD is designed to catch.1 ...