* The `spec.SecurityContext.Sysctls` field is now dropped during creation of `Pod` objects unless the `Sysctls` feature gate is enabled. ([#72752](https://github.com/kubernetes/kubernetes/pull/72752), [@rajathagasthya](https://github.com/rajathagasthya))
    * The `spec.AllowedUnsafeSysctls` and `spec.ForbiddenSysctls` fields are now dropped during creation of `PodSecurityPolicy` objects unless the `Sysctls` feature gate is enabled.

- Kubeadm: remove the deprecated `--csr-only` and `--csr-dir` flags...

- Fixed tracking of terminating Pods in the Job status. The field was not updated unless there were other changes to apply. ([#121342](https://github.com/kubernetes/kubernetes/pull/121342), [@dejanzele](https://github.com/dejanzele))

- kube-controller-manager and cloud-controller-manager now hold generated serving certificates in-memory unless a writeable location is specified with --cert-dir ([#69884](https://github.com/kubernetes/kubernetes/pull/69884), [@liggitt](https://github.com/liggitt))

* `kubectl certificate approve|deny` will not modify an already approved or denied CSR unless the `--force` flag is provided. ([#61971](https://github.com/kubernetes/kubernetes/pull/61971), [@smarterclayton](https://github.com/smarterclayton))

* Admission control support for versioned configuration files ([#39109](https://github.com/kubern...

Some upgrade methods might upgrade etcd from 3.0 to 3.1 automatically when you upgrade from Kubernetes 1.8, unless you specify otherwise. Because [etcd does not support downgrading](https://coreos.com/etcd/docs/latest/upgrades/upgrade_3_1.html), you'll need to either remain on etcd 3.1 or restore from a backup if you want to downgrade back to Kubernetes 1.8.

 - Kubeadm: during "init" an empty cgroupDriver value in the KubeletConfiguration is now always set to "systemd" unless the user is explicit about it. This requires existing machine setups to configure the container runtime to use the "systemd" driver. Documentation on this topic can be found here: https://kubernetes.io/docs/setup/production-environment/container-runtimes/....

- InPlacePodVerticalScaling: Memory limits cannot be decreased unless the memory resize restart policy is set to `RestartContainer`. Container resizePolicy is no longer mutable. ([#130183](https://github.com/kubernetes/kubernetes/pull/130183), [@tallclair](https://github.com/tallclair)) [SIG Apps and Node]

- Enabled use of pods with volumes and user namespaces....