Microsoft 365 Copilot is once again under scrutiny after cybersecurity researchers uncovered multiple vulnerabilities capable of exposing sensitive enterprise information. The flaws, affecting Microsoft’s AI-powered productivity assistant, demonstrate how prompt injection and information disclosure weaknesses can potentially allow attackers to retrieve confidential business data, internal communications, and protected documents without proper authorization.

Security experts warn that these vulnerabilities highlight a growing challenge facing enterprise AI systems: balancing productivity with data protection. As AI copilots gain access to emails, SharePoint files, Teams conversations, and cloud documents, even a small security flaw can create a large attack surface for cybercriminals.

According to recently published security advisories, several vulnerabilities in Microsoft 365 Copilot could allow attackers to exploit weaknesses in how the AI assistant processes prompts and user input. One of the major concerns is the possibility of “prompt injection” attacks, where malicious instructions hidden inside emails, files, or chats manipulate the AI into revealing confidential data.

One disclosed vulnerability, tracked as CVE-2025-53774, impacts Microsoft 365 Copilot Chat (BizChat). Researchers said the flaw could allow unauthorized users to access sensitive information through improper command handling and insufficient input validation. The vulnerability reportedly affects how Copilot processes specially crafted instructions embedded within enterprise workflows.

Another recently documented issue, CVE-2026-26133, involves AI command injection attacks that could expose internal company data through network-based exploitation techniques. Researchers noted that attackers may not require advanced privileges to trigger these attacks, making the vulnerability particularly dangerous in large enterprise environments.

Cybersecurity analysts say the risks are amplified because Microsoft 365 Copilot integrates deeply across Microsoft services, including Outlook, Teams, OneDrive, SharePoint, Excel, and Word. If permissions are not carefully managed, Copilot may unintentionally surface sensitive data that users technically have access to but would not normally discover manually.

Researchers behind the “EchoLeak” study previously demonstrated how attackers could exploit prompt injection weaknesses in Microsoft 365 Copilot using a specially crafted email. The attack reportedly enabled remote exfiltration of sensitive data without requiring direct user interaction, making it one of the first real-world “zero-click” prompt injection exploits targeting enterprise AI systems.

The study explained that attackers could chain multiple bypass techniques together to evade existing protections and manipulate Copilot into leaking privileged information. These attacks represent a new generation of AI-native threats where malicious instructions are hidden inside seemingly legitimate content.

Security researchers have also warned that organizations deploying AI copilots often underestimate the risks associated with over-permissioned environments. In many cases, employees unknowingly have access to more documents and internal resources than necessary. Since Copilot operates using existing user permissions, the AI assistant can potentially retrieve and summarize confidential data scattered across the organization.

Industry experts believe this issue extends beyond Microsoft alone. As enterprises rapidly adopt generative AI tools, attackers are increasingly focusing on prompt injection, data leakage, and AI manipulation techniques. AI assistants now act as centralized gateways to sensitive corporate knowledge, making them attractive targets for cybercriminals.

Microsoft has acknowledged the growing threat landscape surrounding AI systems and continues to improve security protections across its ecosystem. The company recently emphasized AI security monitoring, asset mapping, and advanced threat detection capabilities within Microsoft Defender to help organizations secure AI-powered workflows.

Cybersecurity professionals recommend several immediate mitigation strategies for organizations using Microsoft 365 Copilot:

• ▸Review and restrict unnecessary user permissions.
• ▸Apply strict data classification and sensitivity labels.
• ▸Monitor Copilot interactions for unusual queries.
• ▸Enable advanced logging and auditing.
• ▸Train employees to recognize prompt injection attempts.
• ▸Segment sensitive information away from general AI access.
• ▸Implement Zero Trust security principles.

Experts also advise organizations to perform regular audits of SharePoint, Teams, and OneDrive permissions to reduce the risk of excessive data exposure. In many enterprise environments, years of permission sprawl have created hidden security gaps that AI systems can unintentionally amplify.
The rise of AI-powered workplace tools is transforming productivity, but security researchers warn that organizations must adapt their cybersecurity strategies just as quickly. Traditional security models were not designed for AI systems capable of aggregating and summarizing enormous amounts of enterprise data in seconds.

As Microsoft 365 Copilot adoption continues to expand globally, these vulnerabilities serve as a reminder that AI convenience can also introduce significant cybersecurity risks if governance and access controls are not carefully implemented.