# TopicAttack: An Indirect Prompt Injection Attack via Topic Transition

arXiv: https://arxiv.org/abs/2507.13686 · HTML: https://mlsanity.com/paper/2507.13686/

## Key facts

- Cited by 17 papers in the map (data through 14 Oct 2026).
- Placed in Prompt injection and agent security, one of 12 directions in LLM safety and security.
- Builds on 30 of its 48 references that are in the map.
- First posted on arXiv 18 Jul 2025.

## Placed in

- LLM safety and security / [Prompt injection and agent security](https://mlsanity.com/safety/prompt-injection-and-agent-security/)

## Builds on (most cited first, 30 of 30)

- [PyTorch: An Imperative Style, High-Performance Deep Learning Library](https://mlsanity.com/paper/1912.01703/) (2019)
- [The Llama 3 Herd of Models](https://mlsanity.com/paper/2407.21783/) (2024)
- [Evaluating Large Language Models Trained on Code](https://mlsanity.com/paper/2107.03374/) (2021)
- [Direct Preference Optimization: Your Language Model is Secretly a Reward Model](https://mlsanity.com/paper/2305.18290/) (2023)
- [Towards Deep Learning Models Resistant to Adversarial Attacks](https://mlsanity.com/paper/1706.06083/) (2017)
- [Large Language Models are Zero-Shot Reasoners](https://mlsanity.com/paper/2205.11916/) (2022)
- [SQuAD: 100,000+ Questions for Machine Comprehension of Text](https://mlsanity.com/paper/1606.05250/) (2016)
- [TriviaQA: A Large Scale Distantly Supervised Challenge Dataset for Reading Comprehension](https://mlsanity.com/paper/1705.03551/) (2017)
- [Not what you've signed up for: Compromising Real-World LLM-Integrated Applications with Indirect Prompt Injection](https://mlsanity.com/paper/2302.12173/) (2023)
- [Ignore Previous Prompt: Attack Techniques For Language Models](https://mlsanity.com/paper/2211.09527/) (2022)
- [InjecAgent: Benchmarking Indirect Prompt Injections in Tool-Integrated Large Language Model Agents](https://mlsanity.com/paper/2403.02691/) (2024)
- [The Instruction Hierarchy: Training LLMs to Prioritize Privileged Instructions](https://mlsanity.com/paper/2404.13208/) (2024)
- [StruQ: Defending Against Prompt Injection with Structured Queries](https://mlsanity.com/paper/2402.06363/) (2024)
- [Defending Against Indirect Prompt Injection Attacks With Spotlighting](https://mlsanity.com/paper/2403.14720/) (2024)
- [Benchmarking and Defending Against Indirect Prompt Injection Attacks on Large Language Models](https://mlsanity.com/paper/2312.14197/) (2023)
- [SecAlign: Defending Against Prompt Injection with Preference Optimization](https://mlsanity.com/paper/2410.05451/) (2024)
- [Optimization-based Prompt Injection Attack to LLM-as-a-Judge](https://mlsanity.com/paper/2403.17710/) (2024)
- [Machine Against the RAG: Jamming Retrieval-Augmented Generation with Blocker Documents](https://mlsanity.com/paper/2406.05870/) (2024)
- [RTBAS: Defending LLM Agents Against Prompt Injection and Privacy Leakage](https://mlsanity.com/paper/2502.08966/) (2025)
- [Evaluating the Instruction-Following Robustness of Large Language Models to Prompt Injection](https://mlsanity.com/paper/2308.10819/) (2023)
- [Signed-Prompt: A New Approach to Prevent Prompt Injection Attacks Against LLM-Integrated Applications](https://mlsanity.com/paper/2401.07612/) (2024)
- [Can Indirect Prompt Injection Attacks Be Detected and Removed?](https://mlsanity.com/paper/2502.16580/) (2025)
- [Towards Reasoning in Large Language Models via Multi-Agent Peer Review Collaboration](https://mlsanity.com/paper/2311.08152/) (2023)
- [UniGraph2: Learning a Unified Embedding Space to Bind Multimodal Graphs](https://mlsanity.com/paper/2502.00806/) (2025)
- [GuardReasoner-VL: Safeguarding VLMs via Reinforced Reasoning](https://mlsanity.com/paper/2505.11049/) (2025)
- [Defense Against Prompt Injection Attack by Leveraging Attack Techniques](https://mlsanity.com/paper/2411.00459/) (2024)
- [FiDeLiS: Faithful Reasoning in Large Language Model for Knowledge Graph Question Answering](https://mlsanity.com/paper/2405.13873/) (2024)
- [KnowPhish: Large Language Models Meet Multimodal Knowledge Graphs for Enhancing Reference-Based Phishing Detection](https://mlsanity.com/paper/2403.02253/) (2024)
- [PhishAgent: A Robust Multimodal Agent for Phishing Webpage Detection](https://mlsanity.com/paper/2408.10738/) (2024)
- [Tricking Retrievers with Influential Tokens: An Efficient Black-Box Corpus Poisoning Attack](https://mlsanity.com/paper/2503.21315/) (2025)

## Built on by (most cited first, 17 of 17)

- [AutoDojo: Adaptive Black-Box Attacks Reveal the Limits of IPI Defenses and Task-Specification Effects in LLM Agents](https://mlsanity.com/paper/2606.15057/) (2026)
- [WARD: Adversarially Robust Defense of Web Agents Against Prompt Injections](https://mlsanity.com/paper/2605.15030/) (2026)
- [WebAgentGuard: A Reasoning-Driven Guard Model for Detecting Prompt Injection Attacks in Web Agents](https://mlsanity.com/paper/2604.12284/) (2026)
- [Securing LLM Agents Need Intent-to-Execution Integrity](https://mlsanity.com/paper/2605.16976/) (2026)
- [Plant, Persist, Trigger: Sleeper Attack on Large Language Model Agents](https://mlsanity.com/paper/2605.28201/) (2026)
- [WebTrap: Stealthy Mid-Task Hijacking of Browser Agents During Navigation](https://mlsanity.com/paper/2605.08310/) (2026)
- [Reasoning Hijacking: The Fragility of Reasoning Alignment in Large Language Models](https://mlsanity.com/paper/2601.10294/) (2026)
- [AliMark: Enhancing Robustness of Sentence-Level Watermarking Against Text Paraphrasing](https://mlsanity.com/paper/2605.29434/) (2026)
- [ChatGPT: Excellent Paper! Accept It. Editor: Imposter Found! Review Rejected](https://mlsanity.com/paper/2512.20405/) (2025)
- [Clouding the Mirror: Stealthy Prompt Injection Attacks Targeting LLM-based Phishing Detection](https://mlsanity.com/paper/2602.05484/) (2026)
- [Adversarial Reframing: A Framework for Targeted Generation in Language Models](https://mlsanity.com/paper/2605.21674/) (2026)
- [WebMCP Tool Surface Poisoning: Runtime Manipulation Attacks on LLM Agents](https://mlsanity.com/paper/2606.06387/) (2026)
- [KidnapRAG: A Black-Box Attack for Hijacking Reasoning in Agentic Retrieval-Augmented Generation Systems](https://mlsanity.com/paper/2607.00422/) (2026)
- [Know Your Agent: Reconnaissance-Driven Pentesting of AI Agents](https://mlsanity.com/paper/2607.19837/) (2026)
- [WebMCP-Phalanx: Enforcing and Characterizing Trust Boundaries for Browser-Integrated LLM Agents](https://mlsanity.com/paper/2608.24017/) (2026)
- [MechAudit-40: White-Box Auditing across 40 LLM Attack Mechanisms](https://mlsanity.com/paper/2609.06612/) (2026)
- [TRACER: Trace-Regularized Training Against Indirect Prompt Injection](https://mlsanity.com/paper/2610.19133/) (2026)

## Abstract (arXiv)

Large language models (LLMs) have shown remarkable performance across a range of NLP tasks. However, their strong instruction-following capabilities and inability to distinguish instructions from data content make them vulnerable to indirect prompt injection attacks. In such attacks, instructions with malicious purposes are injected into external data sources, such as web documents. When LLMs retrieve this injected data through tools, such as a search engine and execute the injected instructions, they provide misled responses. Recent attack methods have demonstrated potential, but their abrupt instruction injection often undermines their effectiveness. Motivated by the limitations of existing attack methods, we propose TopicAttack, which prompts the LLM to generate a fabricated conversational transition prompt that gradually shifts the topic toward the injected instruction, making the injection smoother and enhancing the plausibility and success of the attack. Through comprehensive experiments, TopicAttack achieves state-of-the-art performance, with an attack success rate (ASR) over 90% in most cases, even when various defense methods are applied. We further analyze its effectiveness by examining attention scores. We find that a higher injected-to-original attention ratio leads to a greater success probability, and our method achieves a much higher ratio than the baseline methods.