Microsoft Copilot Bug Exposed Confidential Emails
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- Microsoft confirmed a bug in Copilot Chat allowed its AI to read and summarize customers' confidential emails for weeks, bypassing data loss prevention policies meant to block sensitive data from reaching its large language models.
- The vulnerability has been active since January and specifically affected draft and sent email messages with confidential labels applied, which were incorrectly processed by Microsoft 365 Copilot Chat.
- Microsoft began rolling out a fix in early February, trackable by enterprise admins as bug CW1226324.
- A Microsoft spokesperson declined to disclose how many customers were affected by the email exposure.
- The bug was first reported by Bleeping Computer, which flagged that Copilot was ingesting sensitive email content even when customers had policies to prevent exactly that.
- The European Parliament's IT department blocked built-in AI features on lawmakers' work-issued devices, citing concerns that AI tools could upload confidential correspondence to the cloud.
Why it matters: Paying Microsoft 365 customers who configured data loss prevention specifically to keep sensitive emails out of AI processing had those guardrails silently bypassed for weeks, and Microsoft won't quantify the exposure. With the European Parliament already disabling Copilot-style features over parallel cloud concerns, the episode gives enterprise security teams and regulators a concrete data point to challenge Microsoft's AI data handling claims.
