MICROSOFT 365 COPILOT – ARBITRARY DATA EXFILTRATION VIA MERMAID DIAGRAMS

Summary from the TLDR InfoSec newsletter

Microsoft 365 Copilot was vulnerable to a security flaw that allowed sensitive business data, like recent emails, to be exfiltrated using specially crafted documents. Attackers could embed hidden instructions and a fake login button, which used Mermaid diagrams to send encoded company data to servers under their control if a user clicked the button. Microsoft fixed the vulnerability by disabling interactions with dynamic Mermaid diagram content, effectively closing this exfiltration route.