Reprompt Attack: A New Threat to Microsoft Copilot

In the ever-evolving world of technology, security vulnerabilities are an unfortunate reality. One such vulnerability has recently come to light, affecting Microsoft's Copilot AI assistant. Dubbed "Reprompt," this attack method requires only a single click to execute, potentially allowing threat actors to steal sensitive user data.

Understanding Reprompt

According to Varonis Threat Labs' research, Reprompt exploits the 'q' URL parameter to inject malicious instructions into Copilot. This allows an attacker to request and exfiltrate data even after the Copilot chat is closed. The attack chain consists of three techniques: Parameter 2 Prompt (P2P injection), double-request, and chain-request.

Parameter 2 Prompt (P2P injection)

By exploiting the 'q' URL parameter, an attacker can fill a prompt from a URL and inject malicious instructions, forcing Copilot to perform actions, including data exfiltration.

Double-request and Chain-request

The double-request technique takes advantage of Copilot's safeguards against direct data exfiltration or leaks. Repeating a request for an action twice will force it to be performed. Once the initial prompt (repeated twice) is executed, the Reprompt attack chain server issues follow-up instructions and requests, such as demands for additional information.

Impact and Response

Microsoft was notified of the Reprompt vulnerability on Aug. 31, 2025, and patched it prior to public disclosure. The company has confirmed that enterprise users of Microsoft 365 Copilot are not affected. However, users of the personal version should exercise caution.

Staying Safe in the Digital Age

Given the prevalence of security issues in new technologies, it's essential to remain vigilant. Users should be cautious when clicking links, especially from untrusted sources. Additionally, they should be wary of sharing sensitive or personal information and monitor AI assistants for any unusual behavior or strange prompts.

Implications for North East India and Beyond

The Reprompt attack underscores the importance of cybersecurity in the digital age, especially as AI assistants become more prevalent. As more and more services move online, it's crucial for users in North East India and across India to stay informed about potential threats and take steps to protect their data.

Looking Forward

The Reprompt attack represents a broader class of critical AI assistant vulnerabilities driven by external input. As such, it's essential for AI vendors and users to implement validation and safety controls throughout the full process chain, reduce the risk of prompt chaining and repeated actions, and continually monitor for suspicious activity.