Microsoft Copilot Studio Patch Can't Stop Data Leaks

Microsoft patched CVE-2026-21520, a CVSS 7.5 indirect prompt injection vulnerability in Copilot Studio, discovered by Capsule Security and deployed January 15. The CVE is notable for being assigned to an agent-building platform, not just a productivity tool, signaling a new vulnerability class enterprises must track. Capsule also found PipeLeak, a parallel vulnerability in Salesforce Agentforce, highlighting a broader problem: prompt injection in agentic systems cannot be fully eliminated through patches alone. Data exfiltration remains possible even after fixes are applied.