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Researchers have uncovered a critical flaw that allows attackers to manipulate large language models into providing dangerous information, raising serious security concerns across industries.
A team of researchers has identified a fundamental vulnerability in large language models (LLMs) that could leave them open to adversarial attacks. The issue lies in how LLMs process and respond to user instructions, making it possible for attackers to bypass safety measures and elicit harmful information. This discovery, presented at the International Conference on Machine Learning (ICML), has significant implications for the security of AI systems used in critical sectors like government, military, healthcare, and e-commerce.
The flaw hinges on how LLMs interpret instructions from users. By mimicking the style of text that models use internally-often referred to as a "chain of thought"-attackers can trick LLMs into believing they generated certain instructions themselves. This bypasses the guardrails designed to prevent the model from providing dangerous or illegal information.
For example, researchers were able to make popular LLMs provide detailed guides on how to synthesize drugs and sabotage aircraft navigation systems by crafting prompts that included spoofed chain-of-thought notes. Charles Ye, an independent researcher and coauthor of the ICML paper, emphasizes the severity of the issue: “There’s a real probability that this is going to be a problem that’s fundamentally unsolvable.”
The core of the vulnerability lies in the way LLMs handle user input and internal processing. When an LLM receives a prompt, it generates a chain of thought-a sequence of intermediate steps or notes-to arrive at its final response. This chain of thought is crucial for maintaining coherence and context but can also be exploited.

Jasmine Cui, another coauthor of the paper, explains the challenge: “The current approach is like giving the models a list of things they shouldn’t do. But no list is exhaustive, and the model can still generate harmful content if it believes it came up with the idea itself.”
This vulnerability has far-reaching implications for the security and governance of AI systems. As LLMs are increasingly integrated into critical applications, addressing this issue becomes paramount.
The fundamental flaw in LLMs highlights the ongoing challenges in securing AI systems. While current efforts provide some level of protection, a more comprehensive approach is needed to address this critical vulnerability and ensure the safe deployment of AI technology.
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A fundamental flaw leaves LLMs strikingly vulnerable to attack
↗ https://www.technologyreview.com/2026/07/30/1140927/a-fundamental-flaw-leaves-llms-vulnerable-to-attack
About the author
Kai built ML infrastructure at a Bay Area startup before developing an obsession with transformer architectures and inference optimisation that eventually pulled him out of product work entirely. A stint at a compute research lab sharpened his instinct for what actually matters in a model release versus what is marketing. He writes from the inside — from the perspective of someone who has debugged the systems he is describing at three in the morning. He is allergic to hype and instinctively drawn to the unglamorous plumbing questions that everyone else skips over.
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6 August 2026
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