A missing authentication flaw in Microsoft 365 Copilot (CVE-2026-54130) allows an unauthenticated attacker to access sensitive information over a network without any credentials. Because Copilot integrates deeply with organisational data sources such as emails, documents, and Teams conversations, the potential exposure of confidential business data is significant. Microsoft has disclosed this as a high-priority vulnerability requiring attention from organisations using M365 Copilot.

Security Architect’s Take: Review your M365 Copilot deployment and apply any available Microsoft patches or mitigations immediately; in the interim, consider restricting Copilot access to trusted network segments or enforcing Conditional Access policies to reduce the attack surface until a fix is confirmed in place.

Original advisory: CVE-2026-54130 M365 Copilot Information Disclosure Vulnerability