When Convenience Becomes Risk: A Semantic View of Under-Specification in Host-Acting Agents

TL;DR

This paper highlights the security risks of under-specified goal instructions in host-acting agents, proposing a semantic threat model and defense principles to improve safety and control.

Contribution

It introduces a semantic threat model, taxonomy of risky completion patterns, and defense principles for managing goal translation in host-acting agents.

Findings

Semantic under-specification can lead to risky execution plans.

Explicitly defining execution boundaries reduces security risks.

Case study and analysis demonstrate the importance of controlling goal translation.

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.