A Microsoft Copilot security flaw exposed a hidden input that researchers linked to an attack chain, according to Ars Technica. The report says the issue could help attackers steal passwords after a target clicked a link.
The case matters because AI assistants often rely on hidden system prompts, parameters, or instructions that users are not supposed to see. When those internal controls leak, attackers may learn how to steer the system around its intended boundaries.
The reported attack also shows why AI security is not limited to whether a chatbot gives a dangerous answer. It can involve ordinary web actions, links, credentials, and the way an assistant handles instructions from untrusted content.
The details are specific to the reported Copilot flaw, but the broader lesson applies to agentic software. Hidden instructions are not a security boundary by themselves. Systems that can read pages, summarize messages, or act on behalf of users need separate defenses for malicious content and credential exposure.