Yealink YMCS before 2025-05-26 does not prevent OpenAPI access by frozen enterprise accounts, allowing unauthorized access to deactivated interfaces.
https://www.yealink.com/en/trust-center/security-advisories/1318c5efb82e4526
https://support.yealink.com/en/portal/knowledge/show?id=646b44278ef325311f38303f