“Reprompt” attack lets attackers steal data from Microsoft Copilot

Reprompt is a prompt-injection vulnerability against Microsoft Copilot Personal where an attacker hides malicious instructions in the q URL parameter; Copilot auto-executes those prompts in an authenticated session, allowing actions and potential data exfiltration. Microsoft released a patch in January 2026 and no active exploitation was reported; mitigation includes installing the patch, using managed Copilot (with DLP/auditing), and avoiding unsolicited links.