PIIGuard: Mitigating PII Harvesting under Adversarial Sanitization

Mingshuo Liu, Yiwei Zha, Min Chen

Abstract

Browsing-enabled LLM assistants can fetch webpages and answer contact-seeking queries, creating a practical channel for scraping contact-style personally identifiable information (PII) from public pages. Many prior defenses are deployed at the model, service, or agent layer rather than at the webpage itself, leaving ordinary page owners with limited deployable options. We present PIIGuard, a webpage-level defense that repurposes indirect prompt injection as a protective mechanism: the page owner

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Cite This Resource

@article{llmsec202600125,
  title = {PIIGuard: Mitigating PII Harvesting under Adversarial Sanitization},
  author = {Mingshuo Liu and Yiwei Zha and Min Chen},
  year = {2026},
  url = {https://arxiv.org/abs/2605.03129},
}