really, you MUST read this before you upgrade)

- Kube-proxy's IPVS proxy mode no longer sets the net.ipv4.conf.all.route_localnet sysctl parameter. Nodes upgrading will have net.ipv4.conf.all.route_localnet set to 1 but new nodes will inherit the system default (usually 0). If you relied on any behavior requiring net.ipv4.conf.all.route_localnet, you must set ensure it is enabled as kube-proxy will no longer set it automatically. This change helps to further mitigate CVE-2020-8558. ([...

Kubernetes v1.5, `kubectl apply` has had an alpha-stage `--prune` flag to support deleting previously applied objects that have been removed from the input manifest. This feature has remained in alpha ever since due to performance and correctness issues inherent in its design. This PR exposes a second, independent pruning alpha powered by a new standard named `ApplySets`. An `ApplySet` is a server-side object (by default, a Secret; ConfigMaps are also allowed) that kubectl can use to accurately and efficiently...

* Mark image as deliberately optional in v1 Container struct.  Many objects in the Kubernetes API inherit the container struct and only Pods require the field to be set. ([#48406](https://github.com/kubernetes/kubernetes/pull/48406), [@gyliu513](https://github.com/gyliu513))

- Graceful node shutdown, allow the actual inhibit delay to be greater than the expected inhibit delay. ([#103137](https://github.com/kubernetes/kubernetes/pull/103137), [@wzshiming](https://github.com/wzshiming))

- Fixed regression in CPUManager that it will release exclusive CPUs in app containers inherited from init containers when the init containers were removed. ([#104837](https://github.com/kubernetes/kubernetes/pull/104837), [@eggiter](https://github.com/eggiter))