Reprompt Attack Enables Single-Click Data Exfiltration From Microsoft Copilot

Reprompt Attack Enables Single-Click Data Exfiltration From Microsoft Copilot

Cybersecurity researchers have disclosed a new attack method, dubbed Reprompt, that allows attackers to exfiltrate sensitive data from AI chatbots like Microsoft Copilot with a single click. The attack bypasses enterprise security controls and doesn’t require user interaction beyond that initial click, leveraging the “q” URL parameter for indirect prompt injection.

Why This Matters

Current AI security models rely on guardrails to prevent data leaks, but these are often only applied to the initial user request. Reprompt circumvents these safeguards by chaining requests through a server, creating a hidden channel for continuous data exfiltration. The potential scale of data loss is significant, as the server can request any information accessible to Copilot, leading to substantial financial and reputational damage.

Key Insights

• Reprompt Technique: Uses the “q” URL parameter for indirect prompt injection, bypassing initial security checks.
• AI Trust Issues: The attack highlights the inherent difficulty AI systems have in distinguishing between legitimate user input and malicious instructions embedded in requests.
• Emerging Attack Landscape: Numerous recent vulnerabilities like ZombieAgent, Lies-in-the-Loop, and GeminiJack demonstrate a growing trend of adversarial techniques targeting AI-powered tools.

Practical Applications

• Use Case: A threat actor could send a seemingly benign Copilot link via email, initiating a silent data exfiltration process upon a user’s click.
• Pitfall: Assuming initial prompt inspection is sufficient security; the real malicious instructions are hidden in subsequent server requests.

References:

• https://thehackernews.com/2026/01/researchers-reveal-reprompt-attack.html