When Convenience Becomes Risk: A Semantic View of Under-Specification in Host-Acting Agents
Abstract
Host-acting agents promise a convenient interaction model in which users specify goals and the system determines how to realize them. We argue that this convenience introduces a distinct security problem: semantic under-specification in goal specification. User instructions are typically goal-oriented, yet they often leave process constraints, safety boundaries, persistence, and exposure insufficiently specified. As a result, the agent must complete missing execution semantics before acting, and this completion can produce risky host-side plans even when the user-stated goal is benign. In this paper, we develop a semantic threat model, present a taxonomy of semantic-induced risky completion patterns, and study the phenomenon through an OpenClaw-centered case study and execution-trace analysis. We further derive defense design principles for making execution boundaries explicit and constraining risky completion. These findings suggest that securing host-acting agents requires governing not only which actions are allowed at execution time, but also how goal-only instructions are translated into executable plans.
Keywords
Cite
@article{arxiv.2603.21231,
title = {When Convenience Becomes Risk: A Semantic View of Under-Specification in Host-Acting Agents},
author = {Di Lu and Yongzhi Liao and Xutong Mu and Lele Zheng and Ke Cheng and Xuewen Dong and Yulong Shen and Jianfeng Ma},
journal= {arXiv preprint arXiv:2603.21231},
year = {2026}
}