LongPIBench: A Long-Context Benchmark for Prompt Injection

• URL: http://arxiv.org/abs/2608.28411v1
• Date: Fri, 28 Aug 2026 15:00:33 GMT
• Title: LongPIBench: A Long-Context Benchmark for Prompt Injection
• Abstract summary: LongPIBench is a benchmark for evaluating prompt injection defenses in long-context scenarios.<n>We show that even simple prompt injection attacks achieve high success rates and frequently bypass state-of-the-art defenses.
• Score: 52.0498674763688
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Prompt injection attacks pose a serious security risk to large language models in real-world applications. However, existing prompt injection benchmarks primarily focus on short-context inputs, leaving the attacks and defenses in long-context settings largely unexplored. This gap leads to a substantial overestimation of the effectiveness of current defenses. In this paper, we bridge the gap by introducing LongPIBench, a long-context benchmark for prompt injection covering 4 realistic application scenarios: paper peer review, resume screening, code review, and email summary. For each scenario, we construct a synthetic dataset and a real-world dataset, with context lengths ranging from thousands to tens of thousands of tokens. The evaluation results on LongPIBench reveal significant vulnerabilities of prompt injection defenses under long-context settings: even simple heuristic prompt injection attacks achieve high success rates and frequently bypass state-of-the-art defenses. We hope LongPIBench can serve as a practical benchmark for systematically evaluating prompt injection defenses in realistic long-context scenarios.

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