Web-agent harnesses stay vulnerable across prompt and page attacks
Original title: Harness Matters: Measuring and Dissecting Security Resilience in Web Agents
WebTrap Farm separates defensive failures from task limits and finds harness design, not only the model, shapes outcomes.
Researchers model web-agent harnesses as goal interpretation, webpage perception, planning, and action execution. WebTrap Farm tests malicious user prompts, prompt injection, and deceptive web design, using paired usability tasks. They report unsafe behavior even without explicit attack content and say both harness and backend model significantly affect security.
Unconfirmed: Vulnerability findings come from the authors' WebTrap Farm evaluation, not from reported field incidents.
- Some unsafe actions occurred even without explicit attack content.
- Statistical analysis attributes outcomes jointly to the harness and backend model.
- The study localizes defensive behavior across the four workflow stages.
From the original article
1 min read at arxiv.orgWeb agents extend LLMs from text generation to real-world web interaction by relying on execution harnesses that interpret user goals, perceive webpages, plan actions, and ground model decisions into browser operations. While prior work has recognized that agent security depends on more than the backend model alone, how harness design quantitatively shapes web-agent security remains insufficiently measured.
By Xinyi Wu · arxiv.org
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