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In January 2025, security researchers at Aim Labs uncovered a critical zero-click vulnerability in Microsoft 365 Copilot AI, designated as CVE-2025-3271 and dubbed "EchoLeak." This flaw allowed attackers to exfiltrate sensitive user data without any interaction from the victim, marking a significant milestone in the realm of AI security threats.

The image shows a digital display featuring 'Microsoft 365 COF Copilot AI' in a high-tech, futuristic environment.Discovery and Disclosure​

The EchoLeak vulnerability was identified by Aim Labs in early 2025. Upon discovery, the team promptly reported the issue to Microsoft, adhering to responsible disclosure practices. Microsoft acknowledged the report and, by May 2025, had implemented a server-side fix to address the vulnerability. The company confirmed that no customers were impacted and that users did not need to take any action, as the fix was applied automatically. Microsoft also stated that there was no evidence of the vulnerability being exploited in real-world attacks.

Technical Details of EchoLeak​

EchoLeak exploited the integration of Microsoft 365 Copilot AI with email systems. Attackers could craft emails containing hidden prompts designed to manipulate the AI assistant. When a user engaged with Copilot to inquire about topics related to the malicious email, the AI's Retrieval-Augmented Generation (RAG) engine would process the hidden prompts. This process could lead to the unintended extraction and transmission of internal data to external servers controlled by the attackers, all without the user's knowledge or consent.

Implications for AI Security​

The emergence of EchoLeak underscores the potential risks associated with large language models (LLMs) and their integration into enterprise environments. This vulnerability highlights the concept of "LLM Scope Violations," where AI systems can be manipulated to perform actions beyond their intended scope, leading to unauthorized data access and leakage. Such incidents emphasize the need for robust security measures and continuous monitoring when deploying AI-driven tools in sensitive applications.

Broader Context and Related Vulnerabilities​

EchoLeak is not an isolated case. In August 2024, researchers identified a vulnerability in Microsoft 365 Copilot that allowed attackers to steal sensitive user information through a combination of prompt injection and ASCII smuggling techniques. This exploit involved embedding malicious commands within emails or documents, prompting Copilot to perform unauthorized searches and exfiltrate data via concealed Unicode characters in hyperlinks. Microsoft addressed this vulnerability following its disclosure.
Additionally, in August 2024, a server-side request forgery (SSRF) vulnerability, tracked as CVE-2024-38206, was discovered in Microsoft Copilot Studio. This flaw enabled authenticated attackers to bypass SSRF protections, potentially leading to sensitive data leakage across multiple tenants within cloud environments. Microsoft promptly mitigated this issue upon notification.

Microsoft's Response and Mitigation Efforts​

Microsoft has demonstrated a proactive approach in addressing these vulnerabilities. The company has implemented server-side fixes and emphasized that no customers were impacted by these issues. Users are advised to ensure their Microsoft 365 software is updated to benefit from these security patches. Additionally, organizations should exercise caution when interacting with links in documents and emails, especially those from unknown or untrusted sources. Regular monitoring of AI tools like Copilot for unusual behavior is also essential to detect and respond to potential threats promptly.

Conclusion​

The discovery of EchoLeak and similar vulnerabilities serves as a critical reminder of the evolving security challenges posed by AI integration in enterprise environments. As AI systems become more embedded in daily operations, it is imperative for organizations to implement comprehensive risk management strategies, conduct regular security assessments, and foster a culture of cybersecurity awareness to mitigate potential threats effectively.

Source: latestly.com EchoLeak: First-Ever Zero-Click Vulnerability, CVE-2025-3271, Discovered by Aim Labs in Microsoft 365 Copilot AI, Allowed Attackers Steal Sensitive Data Silently, Now Fixed | 📲 LatestLY
 

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