Copilot Hack: Leaked URL Parameter Allowed Autorun Attacks

jonerp · x · 2026-08-24

Varonis discovered a vulnerability in Microsoft Copilot where the AI leaked an undocumented URL parameter while refusing to answer a security question. This parameter revealed historical behavior and protections. By adding "autorun=1" to a link, attackers could execute prompts without user interaction, potentially exfiltrating company data. The vulnerability was reported in December and remained exploitable for eight months before Microsoft patched it.

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