Reprompt Attack: A New Threat to Microsoft Copilot

A recent cybersecurity threat, named "Reprompt," has been making waves, targeting Microsoft's Copilot AI assistant. This attack, unveiled by Varonis Threat Labs, demonstrates the evolving landscape of cyber threats and the need for robust security measures.

Understanding Reprompt

Reprompt is an attack method that requires only a single click to execute, bypassing Copilot's security controls and enabling the theft of user data. The attack is designed to steal sensitive Copilot data, even after the window has been closed.

How Reprompt Works

Reprompt combines three techniques: Parameter 2 Prompt (P2P injection), Double-request, and Chain-request. By exploiting the 'q' URL parameter, an attacker can fill a prompt from a URL and inject malicious instructions, potentially allowing data exfiltration.

Impact on North East India and India at Large

As more businesses and individuals in North East India adopt AI assistants, understanding and mitigating such threats becomes crucial. The Reprompt attack underscores the importance of cybersecurity education and the need for robust security measures to protect sensitive data.

Microsoft's Response

Microsoft was made aware of the Reprompt vulnerability on Aug 31, 2025, and patched it prior to public disclosure. Enterprise users of Microsoft 365 Copilot were not affected.

Staying Safe in the Age of AI Assistants

To stay safe, users should exercise caution when clicking links, especially from untrusted sources. Sharing sensitive or personal information should be done carefully, and users should monitor AI assistants for any unusual behavior or suspicious data requests.

Looking Forward

The Reprompt attack represents a broader class of vulnerabilities in AI assistants. To address this, URL and external inputs should be treated as untrusted, and validation and safety controls should be implemented throughout the process chain.