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Microsoft 365 Copilot Bug Exposes Confidential Emails to AI Summarization

Microsoft 365 Copilot Bug Exposes Confidential Emails to AI Summarization

First seen 18 Feb 2026, 15:24 UTC

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ThreatCluster AI
ThreatCluster March 12, 2026 at 16:10 UTC

Microsoft confirmed a bug in its Copilot AI that allowed unauthorized summarization of customers' confidential emails from late January 2026. The issue affected Microsoft 365 users, bypassing data loss prevention policies designed to protect sensitive information. The bug was first detected on January 21 and involved emails in users' Sent Items and Drafts folders.

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Updated 192d ago How this analysis works

Timeline

2026-01-21
Bug first detected affecting Copilot AI
2026-02-18
Microsoft confirms bug and details its impact

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