WARD: Adversarially Robust Defense of Web Agents Against Prompt Injections

Tri Cao, Yulin Chen, Hieu Cao, Yibo Li, Khoi Le, Thong Nguyen, Yuexin Li, Yufei He, Yue Liu, Shuicheng Yan, Bryan Hooi

Abstract

Web agents can autonomously complete online tasks by interacting with websites, but their exposure to open web environments makes them vulnerable to prompt injection attacks embedded in HTML content or visual interfaces. Existing guard models still suffer from limited generalization to unseen domains and attack patterns, high false positive rates on benign content, reduced deployment efficiency due to added latency at each step, and vulnerability to adversarial attacks that evolve over time or d

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Cite This Resource

@article{llmsec202600093,
  title = {WARD: Adversarially Robust Defense of Web Agents Against Prompt Injections},
  author = {Tri Cao and Yulin Chen and Hieu Cao and Yibo Li and Khoi Le and Thong Nguyen and Yuexin Li and Yufei He and Yue Liu and Shuicheng Yan and Bryan Hooi},
  year = {2026},
  url = {https://arxiv.org/abs/2605.15030},
}