Temporal Leakage in Search-Engine Date-Filtered Web Retrieval: A Retrospective Forecasting Case Study

Fuente: arXiv
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Hauptverfasser: Lahib, Ali El, Xia, Ying-Jieh, Li, Zehan, Wang, Yuxuan, Pi, Xinyu
Format: Preprint
Veröffentlicht: 2026
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author Lahib, Ali El
Xia, Ying-Jieh
Li, Zehan
Wang, Yuxuan
Pi, Xinyu
author_facet Lahib, Ali El
Xia, Ying-Jieh
Li, Zehan
Wang, Yuxuan
Pi, Xinyu
contents Search-engine date filters are widely used to enforce pre-cutoff retrieval in retrospective evaluations of search-augmented forecasters. We show this approach is unreliable across two major search engines: auditing Google Search's before: filter and DuckDuckGo's date-range filter, we find that at least one retrieved page contains major post-cutoff leakage for 71% of questions on Google and 81% on DuckDuckGo, and the answer is directly revealed for 41% and 55%, respectively. Using gpt-oss-120b to forecast with these leaky documents, we demonstrate inflated prediction accuracy (Brier score 0.10 vs. 0.24 with leak-free documents). We characterize recurring leakage mechanisms, including updated articles, related-content modules, unreliable metadata, and absence-based signals, and argue that date-restricted search on these engines is insufficient for credible retrospective evaluation. We recommend stronger retrieval safeguards or evaluation on frozen, time-stamped web snapshots.
format Preprint
id arxiv_https___arxiv_org_abs_2602_00758
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Temporal Leakage in Search-Engine Date-Filtered Web Retrieval: A Retrospective Forecasting Case Study
Lahib, Ali El
Xia, Ying-Jieh
Li, Zehan
Wang, Yuxuan
Pi, Xinyu
Computation and Language
Information Retrieval
I.2.7; H.3.3
Search-engine date filters are widely used to enforce pre-cutoff retrieval in retrospective evaluations of search-augmented forecasters. We show this approach is unreliable across two major search engines: auditing Google Search's before: filter and DuckDuckGo's date-range filter, we find that at least one retrieved page contains major post-cutoff leakage for 71% of questions on Google and 81% on DuckDuckGo, and the answer is directly revealed for 41% and 55%, respectively. Using gpt-oss-120b to forecast with these leaky documents, we demonstrate inflated prediction accuracy (Brier score 0.10 vs. 0.24 with leak-free documents). We characterize recurring leakage mechanisms, including updated articles, related-content modules, unreliable metadata, and absence-based signals, and argue that date-restricted search on these engines is insufficient for credible retrospective evaluation. We recommend stronger retrieval safeguards or evaluation on frozen, time-stamped web snapshots.
title Temporal Leakage in Search-Engine Date-Filtered Web Retrieval: A Retrospective Forecasting Case Study
topic Computation and Language
Information Retrieval
I.2.7; H.3.3
url https://arxiv.org/abs/2602.00758