- Client-go: fixed potential data races retrying requests using a custom `io.Reader` body; with this fix, only requests with no body or with `string` / `[]byte` / `runtime.Object` bodies can be retried ([#113933](https://github.com/kubernetes/kubernetes/pull/113933), [@liggitt](https://github.com/liggitt))

* kube-apiserver: a request body of a CREATE/UPDATE/PATCH/DELETE resource operation larger than 100 MB will return a 413 "request entity too large" error. ([#73805](https://github.com/kubernetes/kubernetes/pull/73805), [@caesarxuchao](https://github.com/caesarxuchao))

* kube-apiserver: a request body of a CREATE/UPDATE/PATCH/DELETE resource operation larger than 100 MB will return a 413 "request entity too large" error. ([#73805](https://github.com/kubernetes/kubernetes/pull/73805), [@caesarxuchao](https://github.com/caesarxuchao))

* kube-apiserver: a request body of a CREATE/UPDATE/PATCH/DELETE resource operation larger than 100 MB will return a 413 "request entity too large" error. ([#73805](https://github.com/kubernetes/kubernetes/pull/73805), [@caesarxuchao](https://github.com/caesarxuchao))

- Limit the body length of exec readiness/liveness probes. remote CRIs and Docker shim read a max of 16MB output of which the exec probe itself inspects 10kb. ([#82514](https://github.com/kubernetes/kubernetes/pull/82514), [@dims](https://github.com/dims))

* The 504 timeout error was returning a JSON error body that indicated it was a 500.  The body contents now correctly report a 500 error. ([#49678](https://github.com/kubernetes/kubernetes/pull/49678), [@smarterclayton](https://github.com/smarterclayton))

- Kube-proxy service health returns http header `X-Load-Balancing-Endpoint-Weight` with number of local endpoints. The same information is still available in response body JSON `payload.LocalEndpoints`. ([#118999](https://github.com/kubernetes/kubernetes/pull/118999), [@cezarygerard](https://github.com/cezarygerard))

* The error handling behavior of `pkg/client/restclient.Result` has changed.  Calls to `Result.Raw()` will no longer parse the body, although they will still return errors that react to `pkg/api/errors.Is*()` as in previous releases.  Callers of `Get()` and `Into()` will continue to receive errors that are parsed from the body if the kind and apiVersion of the body match the `Status` object. ([#36001](https://github.com/kubernetes/kubernetes/pull/36001), [@smarterclayton](https://github.com/smarterclayton))...

### Bug or Regression

- Client-go: fixes potential data races retrying requests using a custom io.Reader body; with this fix, only requests with no body or with string / []byte / runtime.Object bodies can be retried ([#113933](https://github.com/kubernetes/kubernetes/pull/113933), [@liggitt](https://github.com/liggitt)) [SIG API Machinery]

## Changelog since v1.16.0

### Other notable changes

* Limit the body length of exec readiness/liveness probes. remote CRIs and Docker shim read a max of 16MB output of which the exec probe itself inspects 10kb. ([#82514](https://github.com/kubernetes/kubernetes/pull/82514), [@dims](https://github.com/dims))