Learning to Inject: Automated Prompt Injection via Reinforcement Learning

Fuente: arXiv
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Autori principali: Chen, Xin, Zhang, Jie, Tramèr, Florian
Natura: Preprint
Pubblicazione: 2026
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author Chen, Xin
Zhang, Jie
Tramèr, Florian
author_facet Chen, Xin
Zhang, Jie
Tramèr, Florian
contents Prompt injection is one of the most critical vulnerabilities in LLM agents; yet, effective automated attacks remain largely unexplored from an optimization perspective. Existing methods heavily depend on human red-teamers and hand-crafted prompts, limiting their scalability and adaptability. We propose AutoInject, a reinforcement learning framework that generates universal, transferable adversarial suffixes while jointly optimizing for attack success and utility preservation on benign tasks. Our black-box method supports both query-based optimization and transfer attacks to unseen models and tasks. Using only a 1.5B parameter adversarial suffix generator, we successfully compromise frontier systems including GPT 5 Nano, Claude Sonnet 3.5, and Gemini 2.5 Flash on the AgentDojo benchmark, establishing a stronger baseline for automated prompt injection research.
format Preprint
id arxiv_https___arxiv_org_abs_2602_05746
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Learning to Inject: Automated Prompt Injection via Reinforcement Learning
Chen, Xin
Zhang, Jie
Tramèr, Florian
Machine Learning
Artificial Intelligence
Prompt injection is one of the most critical vulnerabilities in LLM agents; yet, effective automated attacks remain largely unexplored from an optimization perspective. Existing methods heavily depend on human red-teamers and hand-crafted prompts, limiting their scalability and adaptability. We propose AutoInject, a reinforcement learning framework that generates universal, transferable adversarial suffixes while jointly optimizing for attack success and utility preservation on benign tasks. Our black-box method supports both query-based optimization and transfer attacks to unseen models and tasks. Using only a 1.5B parameter adversarial suffix generator, we successfully compromise frontier systems including GPT 5 Nano, Claude Sonnet 3.5, and Gemini 2.5 Flash on the AgentDojo benchmark, establishing a stronger baseline for automated prompt injection research.
title Learning to Inject: Automated Prompt Injection via Reinforcement Learning
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2602.05746