Microsoft 365 Copilot Vulnerability Exposed: ASCII Smuggling Risk to User Data
Recently, a significant vulnerability within Microsoft 365 Copilot was identified and subsequently patched, shedding light on an emerging security concern known as ASCII smuggling. This technique, which leverages specific Unicode characters resembling ASCII but remaining nearly invisible in user interfaces, allows malicious actors to manipulate data without detection. Security researcher Johann Rehberger emphasized that attackers can utilize this method to render hidden information within hyperlinks, essentially staging data for illicit exfiltration.
The attack chain involves several sophisticated steps, beginning with a prompt injection initiated through malicious content embedded in shared documents, allowing attackers to seize control of the Copilot chatbot. Once compromised, the Copilot could be instructed to search for sensitive emails and documents using automated tool invocation, further exacerbating the threat. The culmination of the attack hinges on the use of ASCII smuggling, drawing users into clicking deceptive links that potentially lead to unauthorized data transfers to external servers.
The implications of such an exploit are serious, with sensitive user information, including multi-factor authentication (MFA) codes, potentially intercepted and sent to adversary-controlled destinations. Microsoft’s swift action to address these vulnerabilities followed a responsible disclosure in January 2024, yet the incident underscores the urgent need for vigilance regarding AI security risks.
This vulnerability has sparked proof-of-concept attacks demonstrating how Microsoft Copilot can be coerced into providing misleading information, facilitating data exfiltration, and bypassing existing security measures. Researchers from Zenity have further outlined tactics that allow threat actors to execute retrieval-augmented generation (RAG) poisoning and indirect prompt injection, which could lead to remote code execution attacks that fully compromise Microsoft Copilot and similar AI applications. In this scenario, an external attacker could even manipulate Copilot to generate phishing pages designed to deceive users.
Among the most concerning capabilities revealed is the potential for turning the AI chatbot into an effective spear-phishing tool. Utilizing a technique known as LOLCopilot, attackers who gain access to a victim’s email can craft messages that closely mimic the compromised user’s communication style, thereby increasing the likelihood of successful phishing attempts.
Microsoft has additionally acknowledged the risk posed by publicly accessible Copilot bots created without adequate authentication, which could serve as entry points for cybercriminals aiming to extract sensitive information. The company has urged organizations to assess their risk management strategies, focusing on mitigating potential data leaks stemming from these AI systems.
For business owners, the landscape of risks surrounding AI tools underscores the importance of rigorous cybersecurity measures. Enabling Data Loss Prevention (DLP) and implementing other security protocols can help control the creation and deployment of Copilot applications within enterprises. As this vulnerability highlights, maintaining awareness of the tactics and techniques outlined in the MITRE ATT&CK framework will be essential for preempting potential attacks. The incident serves as a crucial reminder of the evolving threat landscape in the realm of AI, where the convergence of technology and cyber vulnerabilities poses significant challenges for organizations worldwide.
