Vulnerable cross-model authorization in juju

Vulnerable cross-model authorization in juju. If a charm's cross-model permissions are revoked or expire, a malicious user who is able to update database records can mint an invalid macaroon that is incorrectly validated by the juju controller, enabling a charm to maintain otherwise revoked or expired permissions. This allows a charm to continue relating to another charm in a cross-model relation, and use their workload without their permission. No fix is available as of the time of writing.