Microsoft 365 Copilot AI Summary Flaw Exposes Emails

A security weakness in Microsoft 365 Copilot is allowing the AI assistant to generate summaries of emails that are marked as confidential. This happens even when Data Loss Prevention (DLP) controls are configured to block access to sensitive content.

Because of this flaw, protected email data may be processed by Copilot and surfaced inside AI chat responses, creating a risk of unintended exposure.

The issue is tracked by Microsoft under reference CW1226324 and was first identified on February 4, 2026. It affects the Copilot “Work Tab” Chat feature.

Vulnerability Details

Field	Details
Tracking Reference	CW1226324
Affected Feature	Copilot “Work Tab” Chat
Security Issue	Bypass of DLP enforcement
Technical Cause	Processing logic defect in folder handling
Impacted Mail Folders	Sent Items, Drafts

Technical Cause and Security Impact

Microsoft’s investigation found that a defect in how Copilot processes certain mail folders is responsible for the issue.

Due to this error, emails stored in Sent Items and Drafts can be accessed by Copilot even if confidentiality sensitivity labels are applied.

Normally, sensitivity labels combined with DLP rules should block AI tools from reading or summarizing restricted emails. However, the defect prevents those protections from being properly enforced for the affected folders.

As a result, confidential information may appear in Copilot-generated summaries.

This is especially concerning for sectors such as healthcare, financial services, and government agencies, where strict email protection is tied to regulatory compliance.

The NHS has internally logged the matter as INC46740412, confirming operational impact within public sector environments.

Allowing an AI system to process labeled content despite DLP rules represents a serious breakdown in data governance controls.

Remediation Status

Microsoft began deploying a fix on February 11, 2026, and is contacting certain affected customers to confirm the resolution.

The update is still rolling out, and not all tenants may have received the fix yet.

Organizations using Microsoft 365 Copilot with email sensitivity labels enabled could be impacted until remediation is fully completed.

Recommended Actions

Administrators should monitor the Microsoft 365 Admin Center for updates related to reference CW1226324.

It is also recommended to review Copilot audit logs for unexpected access to labeled email content.

Until Microsoft confirms full deployment of the fix, organizations handling highly sensitive communications may consider temporarily limiting Copilot access to reduce exposure risk.