Copilot vulnerability lets attackers tamper with audit logs

Recent reports are warning of a vulnerability in Microsoft Copilot integrations that allows attackers to bypass audit logging, and security experts are freaking out. Security pros quickly pointed out that means a malicious actor can do things without leaving a trail in the logs we would expect.

The flaw in Copilot audit logging

Audit logs are the lifeblood of enterprise security. If an organization has any hope of defending against breaches, insider threats, and other areas, they must rely on audit logs to do their investigation. Audit logs allow organizations to hold users accountable for their actions (e.g., logging file access, admin changes, and system queries).

The flaw is what Copilot does, as it happens within Microsoft 365 applications like Outlook, Teams, and Word. For example, after a user interacts with Copilot and asks a question about querying data, not every request and response is logged in the audit logs. Instead, only partial events are logged, and what this means for the security team is there is little visibility for a malicious insider or compromised account operator to use Copilot without alerts tied to any enterprise security monitoring plan.

For example, it’s possible to have an operational interaction with a user querying internal sensitive company data through Copilot. While the activity happens through Copilot, the full request and response may never make it to the audit log, leaving potential gaps in the forensic trail when an investigator tries to trace the user’s actions.

Why attackers care about this loophole

From a hacker’s point of view, this is a goldmine. Imagine getting into a corporate account and quietly pulling financial reports or confidential documents through Copilot. Normally every query to sensitive files would leave a trail. With incomplete logging, attackers can “live off the land” and blend in with normal traffic and avoid detection. Worse, security analysts might only see fragments, such as “user accessed Copilot,” without details on what was asked or retrieved. This is like watching a CCTV camera that records only when someone enters the building but not what they do inside.

Microsoft’s response and mitigation

Microsoft has acknowledged the limitations in Copilot logging and is working on it. Until then, enterprises are advised to layer defenses rather than relying on logs. Recommended steps are:

• Restrict Copilot access to sensitive data sources until full auditing is available.

• Implement anomaly detection to flag unusual Copilot use, such as bulk queries or access outside work hours.

• Educate employees on responsible use of generative AI assistants inside enterprise apps.

What this means for security teams

In summary, this vulnerability highlights a bigger issue: as AI assistants get embedded in business systems, the security controls need to move from basic user actions to AI-based actions that provide a complete and detailed activity log of the underlying impersonation capability that is responsible for the AI actions. When there is a gap between the information and the ability to see it, attackers will pounce. Until Copilot’s audit logging gets better, security teams should treat Copilot as a high-risk blind spot and monitor accordingly.

Key takeaway

The flaw in Copilot’s logging means an attacker can’t get to the data directly. But it hides the information once the attacker is in. For businesses, the threat isn’t just data exfiltration; it’s having a hard time proving or even knowing what was taken.

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