Microsoft Copilot Studio indirect prompt injection (ShareLeak)
Date: 2026-04-15
Affected: Microsoft Copilot Studio
Attack vector: prompt-injection
Category: real-world
Severity: High
CVE: CVE-2026-21520
CWE: CWE-77
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N)

Indirect prompt injection in Copilot Studio (ShareLeak): attacker injects payload via SharePoint form submission that directs the Copilot agent to query SharePoint Lists for customer data and exfiltrate via Outlook to attacker-controlled email. CVSS 7.5. Patched 2026-01-15.


Mitigations:

Architectural layers (MAESTRO):