- JWTs used in service account and OIDC authentication are now strictly parsed to confirm that they use compact serialization. Other encodings were not previously accepted, but would result in different unspecific errors. ([#123540](https://github.com/kubernetes/kubernetes/pull/123540), [@enj](https://github.com/enj))

- Added the feature gate CBORServingAndStorage to allow CBOR as the encoding for API request and response bodies, and as the storage encoding for custom resources. Clients must opt in; programs built with client-go can do this using the client-go feature gates ClientsAllowCBOR and ClientsPreferCBOR. ([#128539](https://github.com/kubernetes/kubernetes/pull/128539),...

- Added support for encoding and decoding types that implement the standard library interfaces `json.Marshaler`, `json.Unmarshaler`, `encoding.TextMarshaler`, or `encoding.TextUnmarshaler` to and from CBOR by transcoding. ([#132935](https://github.com/kubernetes/kubernetes/pull/132935), [@benluddy](https://github.com/benluddy))

- kube-apiserver: fixed a bug that could cause a goroutine leak if the apiserver encountered an encoding error serving a watch to a websocket watcher ([#84693](https://github.com/kubernetes/kubernetes/pull/84693), [@tedyu](https://github.com/tedyu))

* kube-apiserver: fixed a bug that could cause a goroutine leak if the apiserver encountered an encoding error serving a watch to a websocket watcher ([#84693](https://github.com/kubernetes/kubernetes/pull/84693), [@tedyu](https://github.com/tedyu))

* Kubernetes now supports transparent compression of API responses. Clients that send `Accept-Encoding: gzip` will now receive a GZIP compressed response body if the API call was larger than 128KB.  Go clients automatically request gzip-encoding by default and should see reduced transfer times for very large API requests.  Clients in other languages may need to make changes to benefit from compression. ([#77449](http...

### SIG API Machinery

[SIG API Machinery][] is responsible for all aspects of the API server: API registration and discovery, generic API CRUD semantics, admission control, encoding/decoding, conversion, defaulting, persistence layer (etcd), OpenAPI, third-party resources, garbage collection, and client libraries.

be migrated at the current time using the official Kubernetes procedure.

1.6 will also default to protobuf encoding if using etcd3.  **This change is
irreversible.**  To rollback, you must restore from a backup made before the
protobuf/etcd3 switch, and any changes since the backup will be lost.  As 1.5
does not support protobuf encoding, if you roll back to 1.5 after upgrading to

    - Uses debian-base:buster-v1.2.0 ([#94733](https://github.com/kubernetes/kubernetes/pull/94733), [@justaugustus](https://github.com/justaugustus)) [SIG API Machinery, Release and Testing]

- `klog` text output now uses JSON as encoding for structs, maps and slices. ([#117687](https://github.com/kubernetes/kubernetes/pull/117687), [@pohly](https://github.com/pohly))
- `kube-proxy` in iptables mode will now have separate `sync_full_proxy_rules_duration_seconds`\nand