Conor McCauley | Searcharxiv

arXiv2026

IH-Benchmark: A Conflict-Centered Benchmark for Instruction-Hierarchy Robustness in LLM Applications

When a language model receives conflicting instructions from different priority levels, which one does it actually follow? This question lies at the heart of reliable LLM deployment. Existing benchmarks answer this only partially, often focusing on a single hierarchy edge or adapting public datasets with limited tool-use coverage. We present IH-Benchmark, a conflict-centered benchmark for instruction-hierarchy robustness across direct system-user conflicts (S>U) and tool-mediated user-tool (U>T) conflicts. IH-Benchmark is built from a human-authored taxonomy of 44 constraint families across generic, health, finance, retail, and coding settings, and evaluates scenarios with a uniform binary pass/fail protocol combining a predicate DSL with category-scoped LLM judges. Across 37 evaluated models, hierarchy compliance ranges from 98.2% to 20.5%. We find that strong S>U compliance is not a reliable proxy for U>T robustness: several models preserve system constraints under direct user conflict but degrade sharply when conflicting instructions appear in tool outputs. Constraint hardening also reveals a split between models: some failures are largely fixed by stronger warnings, while others persist across all strictness levels. Finally, the most revealing failures are often subtle rather than overtly dangerous; models resist unauthorized purchases or bulk ticket closure more reliably than injected disclaimers or small factual distortions. These results suggest that instruction-hierarchy robustness is not a single capability, but a set of behaviors that must be evaluated across conflict surfaces, constraint types, and attack presentations.

cs.CR↗

arXiv2025

LLMail-Inject: A Dataset from a Realistic Adaptive Prompt Injection Challenge

Indirect Prompt Injection attacks exploit the inherent limitation of Large Language Models (LLMs) to distinguish between instructions and data in their inputs. Despite numerous defense proposals, the systematic evaluation against adaptive adversaries remains limited, even when successful attacks can have wide security and privacy implications, and many real-world LLM-based applications remain vulnerable. We present the results of LLMail-Inject, a public challenge simulating a realistic scenario in which participants adaptively attempted to inject malicious instructions into emails in order to trigger unauthorized tool calls in an LLM-based email assistant. The challenge spanned multiple defense strategies, LLM architectures, and retrieval configurations, resulting in a dataset of 208,095 unique attack submissions from 839 participants. We release the challenge code, the full dataset of submissions, and our analysis demonstrating how this data can provide new insights into the instruction-data separation problem. We hope this will serve as a foundation for future research towards practical structural solutions to prompt injection.

cs.CR↗