Malicious google credential in DNS secret can lead to privilege escalation

Gardener External DNS Management is an environment to manage external DNS entries for a kubernetes cluster. A security vulnerability was discovered in Gardener's External DNS Management prior to version 0.23.6 that could allow a user with administrative privileges for a Gardener project or a user with administrative privileges for a shoot cluster, including administrative privileges for a single namespace of the shoot cluster, to obtain control over the seed cluster where the shoot cluster is managed. This CVE affects all Gardener installations no matter of the public cloud provider(s) used for the seed clusters/shoot clusters. The affected component is `gardener/external-dns-management`. The `external-dns-management` component may also be deployed on the seeds by the `gardener/gardener-extension-shoot-dns-service` extension when the extension is enabled. In this case, all versions of the `shoot-dns-service` extension `<= v1.60.0` are affected by this vulnerability. Version 0.23.6 of Gardener External DNS Management fixes the issue.