SAFEx: Analyzing Vulnerabilities of MoE-Based LLMs via Stable Safety-critical Expert Identification - Lai, Zhenglin; Liao, Mengyao; Wu, Bingzhe; Xu, Dong; Zhao, Zebin; Yuan, Zhihang; Fan, Chao; Li, Jianqiang (Advances in Neural Information Processing Systems, 2025)