@inproceedings{li-etal-2026-multilingual,
title = "Multilingual Safety Signals Are Multi-Layered: Filtering Safety-Degrading Data for Safer {LLM}s",
author = "Li, Jiakun and
Song, Guowei and
Li, Sijia and
He, Xingwei and
Chai, Hongzheng and
Yuan, Yuan",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.1492/",
pages = "34105--34120",
ISBN = "979-8-89176-459-0",
abstract = "Preserving safety alignment during large language models fine-tuning is critical, however, recent studies have demonstrated that even benign fine-tuning data may contain safety-degrading samples that silently undermine such alignment. Existing approaches typically identify safety-degrading samples using representations from a single safety-sensitive layer. However, whether a single safety-sensitive layer is sufficient for identifying such samples in multilingual settings remains unclear, where representation patterns may vary across languages. Our cross-lingual analysis shows that sensitive layers are only partially shared across languages and that safety-relevant signals often span multiple layers. Motivated by these observations, we propose \textsc{MMSafe}, a multi-layer framework for multilingual safety-degrading data identification that jointly leverages shared and language-specific sensitive layers. Extensive experiments across multiple models, languages, and safety benchmarks demonstrate that \textsc{MMSafe} reduces the average harmful-response ratio by 60{\%} compared with random filtering and outperforms the strongest single-layer baseline, demonstrating the effectiveness of multi-layer modeling for robust multilingual safety alignment. Code is available at \url{https://anonymous.4open.science/r/MMSAFE}."
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<abstract>Preserving safety alignment during large language models fine-tuning is critical, however, recent studies have demonstrated that even benign fine-tuning data may contain safety-degrading samples that silently undermine such alignment. Existing approaches typically identify safety-degrading samples using representations from a single safety-sensitive layer. However, whether a single safety-sensitive layer is sufficient for identifying such samples in multilingual settings remains unclear, where representation patterns may vary across languages. Our cross-lingual analysis shows that sensitive layers are only partially shared across languages and that safety-relevant signals often span multiple layers. Motivated by these observations, we propose MMSafe, a multi-layer framework for multilingual safety-degrading data identification that jointly leverages shared and language-specific sensitive layers. Extensive experiments across multiple models, languages, and safety benchmarks demonstrate that MMSafe reduces the average harmful-response ratio by 60% compared with random filtering and outperforms the strongest single-layer baseline, demonstrating the effectiveness of multi-layer modeling for robust multilingual safety alignment. Code is available at https://anonymous.4open.science/r/MMSAFE.</abstract>
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%0 Conference Proceedings
%T Multilingual Safety Signals Are Multi-Layered: Filtering Safety-Degrading Data for Safer LLMs
%A Li, Jiakun
%A Song, Guowei
%A Li, Sijia
%A He, Xingwei
%A Chai, Hongzheng
%A Yuan, Yuan
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F li-etal-2026-multilingual
%X Preserving safety alignment during large language models fine-tuning is critical, however, recent studies have demonstrated that even benign fine-tuning data may contain safety-degrading samples that silently undermine such alignment. Existing approaches typically identify safety-degrading samples using representations from a single safety-sensitive layer. However, whether a single safety-sensitive layer is sufficient for identifying such samples in multilingual settings remains unclear, where representation patterns may vary across languages. Our cross-lingual analysis shows that sensitive layers are only partially shared across languages and that safety-relevant signals often span multiple layers. Motivated by these observations, we propose MMSafe, a multi-layer framework for multilingual safety-degrading data identification that jointly leverages shared and language-specific sensitive layers. Extensive experiments across multiple models, languages, and safety benchmarks demonstrate that MMSafe reduces the average harmful-response ratio by 60% compared with random filtering and outperforms the strongest single-layer baseline, demonstrating the effectiveness of multi-layer modeling for robust multilingual safety alignment. Code is available at https://anonymous.4open.science/r/MMSAFE.
%U https://aclanthology.org/2026.emnlp-main.1492/
%P 34105-34120
Markdown (Informal)
[Multilingual Safety Signals Are Multi-Layered: Filtering Safety-Degrading Data for Safer LLMs](https://aclanthology.org/2026.emnlp-main.1492/) (Li et al., EMNLP 2026)
ACL