Challenge: Considering the vast size and wide-ranging sources of LLMs’ training data, it could explicitly or implicitly include test data.
Approach: They propose a Contamination Detection via output Distribution (CDD) which detects data contamination only by identifying the peakedness of LLM's output distribution.
Outcome: The proposed method improves performance by 21.8%-30.2% on humanEval and TED: trustworthy evaluation via output distribution.

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Towards Data Contamination Detection for Modern Large Language Models: Limitations, Inconsistencies, and Oracle Challenges (2025.coling-main)

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Challenge: Existing methods for detecting data contamination in large language models have limitations and limitations . data contamination occurs when test or evaluation data is exposed to the model during its training phases .
Approach: They evaluate five different methods for detecting data contamination in large language models . they find that current methods have non-trivial limitations in their assumptions and practical applications .
Outcome: The proposed methods have non-trivial limitations and difficulties in detecting contamination . the authors highlight the complexity of contamination detection in advanced LLMs .
DCR: Quantifying Data Contamination in LLMs Evaluation (2025.emnlp-main)

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Challenge: Large language models (LLMs) memorize evaluation data during training, inflating performance metrics and undermining genuine generalization assessment.
Approach: They propose a framework to detect and quantify benchmark data contamination (BDC) by synthesizing contamination scores via a fuzzy inference system.
Outcome: The proposed framework detects and quantifies BDC risk across semantic, informational, data, and label levels.
Controllable Contamination Detection for Reliable LLM Evaluation with Statistical Guarantees (2026.acl-long)

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Challenge: Existing training data detectors fail to detect clean samples from contaminated test sets . existing methods fail to identify clean samples due to black-box nature of LLMs .
Approach: They propose a framework that detects and filters contaminated evaluation data . they propose 'failure detection' to reduce the proportion of contaminated samples mistakenly retained .
Outcome: The proposed framework reduces false discovery rate (FDR) under valid FDR control while maintaining evaluation consistency.
Does Data Contamination Detection Work (Well) for LLMs? A Survey and Evaluation on Detection Assumptions (2025.findings-naacl)

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Challenge: Large language models have demonstrated great performance across various benchmarks, but data contamination is a concern in their evaluation.
Approach: They analyze 50 papers on data contamination detection and test three of them as case studies to identify the possibility of data contamination.
Outcome: The proposed methods can detect membership inference attacks on instance-level data, and can perform similar to random guessing on LLM pretraining datasets.
Benchmarking Large Language Models Under Data Contamination: A Survey from Static to Dynamic Evaluation (2025.emnlp-main)

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Challenge: In the era of evaluating large language models, data contamination is an increasingly prominent concern . static benchmarking has been used for evaluation, but there are limitations of *dynamic* benchmarks .
Approach: They propose a series of optimal design principles for *dynamic* benchmarking and analyze the limitations of existing *static* benchmarks.
Outcome: The proposed benchmarks highlight a critical gap in the evaluation of LLMs.
When Benchmarks Leak: Inference-Time Decontamination for LLMs (2026.acl-long)

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Challenge: a large number of large language models (LLMs) are being evaluated for their performance, but their reliability is threatened by test set contamination.
Approach: They propose a framework that decontaminates large language models by applying small perturbations to the input embedding space.
Outcome: The proposed framework achieves strong decontamination effectiveness while incurring minimal degradation in benign utility.
NLP Evaluation in trouble: On the Need to Measure LLM Data Contamination for each Benchmark (2023.findings-emnlp)

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Challenge: Existing methods for evaluating large language models using annotated benchmarks are in trouble . data contamination can cause wrong scientific conclusions being published .
Approach: They argue that the evaluation of NLP tasks using annotated benchmarks is in trouble . they define different levels of data contamination and propose a community effort .
Outcome: The proposed measures should detect when data from a benchmark was exposed to a model and flag papers with conclusions compromised by data contamination.
Quantifying Contamination in Evaluating Code Generation Capabilities of Language Models (2024.acl-long)

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Challenge: Recent studies have shown that large language models are contaminated with data from pretraining and finetuning tasks.
Approach: They perform extensive analysis on the factors that affect model memorization and generalization, such as model size, problem difficulty, and question length.
Outcome: The results show that models perform better on the subset of the benchmarks where similar solutions are seen during training.
Unveiling the Spectrum of Data Contamination in Language Model: A Survey from Detection to Remediation (2024.findings-acl)

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Challenge: Data contamination is a problem in Large language models due to the reliance on extensive internet-derived training corpora.
Approach: They present a survey on the topic of data contamination in large language models.
Outcome: The results of the first survey on data contamination in large language models provide a comprehensive guide for NLP researchers seeking a systematic understanding of the issue.
Leak, Cheat, Repeat: Data Contamination and Evaluation Malpractices in Closed-Source LLMs (2024.eacl-long)

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Challenge: Lack of access to model details has raised concerns about data contamination among researchers.
Approach: They conduct the first systematic analysis of work using OpenAI’s GPT-3.5 and GPT-4, the most prominently used LLMs today, in the context of data contamination.
Outcome: The proposed models have been exposed to 4.7M samples from 263 benchmarks during the first year after their release.

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