error if it is not available.  Clients may request fallback to the normal object by adding a non-qualified mime-type to their `Accept` header like `application/json` - the server will then respond with either the alternate representation if it is supported or the fallback mime-type which is the normal object response. ([#59059](https://github.com/kubernetes/kubernetes/pull/59059), [@smarterclayton](https://github.com/smarterclayton))

* kube-apiserver now uses SSH tunnels for webhooks if...

* Resolves an issue serving aggregated APIs backed by services that respond to requests to `/` with non-2xx HTTP responses ([#79895](https://github.com/kubernetes/kubernetes/pull/79895), [@deads2k](https://github.com/deads2k))

  The API Server will no longer proxy non-101 responses for upgrade requests. This could break proxied backends (such as an extension API server) that respond to upgrade requests with a non-101 response code. ([#92941](https://github.com/kubernetes/kubernetes/pull/92941), [@tallclair](https://github.com/tallclair)) [SIG API Machinery]
 
## Changes by Kind

* Fixes spurious 0-length API responses. ([#72856](https://github.com/kubernetes/kubernetes/pull/72856), [@liggitt](https://github.com/liggitt))

- Kube-apiserver: redirect responses are no longer returned from backends by default. Set `--aggregator-reject-forwarding-redirect=false` to continue forwarding redirect responses. ([#112331](https://github.com/kubernetes/kubernetes/pull/112331), [@enj](https://github.com/enj)) [SIG API Machinery]

- Fixed a bug that was blocking extensible error handling when serializing API responses error out. Previously, serialization failures always resulted in the status code of the original response being returned. Now, the following behavior occurs: ([#67041](https://github.com/kubernetes/kubernetes/pull/67041), [@tristanburgess](https://github.com/tristanburgess))

onseHeader","getAllResponseHeaders","setRequestHeader","overrideMimeType","mimeType","status","abort","statusText","finalText","crossDomain","host","hasContent","ifModified","headers","beforeSend","success","send","nativeStatusText","responses","isSuccess","response","modified","ct","finalDataType","firstDataType","ajaxHandleResponses","conv2","current","conv","dataFilter","throws","ajaxConvert","getJSON","getScript","text script","wrapAll","firstElementChild","wrapInner","htmlIsFunction","unwra...

onseHeader","getAllResponseHeaders","setRequestHeader","overrideMimeType","mimeType","status","abort","statusText","finalText","crossDomain","host","hasContent","ifModified","headers","beforeSend","success","send","nativeStatusText","responses","isSuccess","response","modified","ct","finalDataType","firstDataType","ajaxHandleResponses","conv2","current","conv","dataFilter","throws","ajaxConvert","getJSON","getScript","text script","wrapAll","firstElementChild","wrapInner","htmlIsFunction","unwra...

- Kube-apiserver: redirect responses are no longer returned from backends by default. Set `--aggregator-reject-forwarding-redirect=false` to continue forwarding redirect responses. ([#112358](https://github.com/kubernetes/kubernetes/pull/112358), [@enj](https://github.com/enj)) [SIG API Machinery]

- Kube-apiserver: redirect responses are no longer returned from backends by default. Set `--aggregator-reject-forwarding-redirect=false` to continue forwarding redirect responses. ([#112359](https://github.com/kubernetes/kubernetes/pull/112359), [@enj](https://github.com/enj)) [SIG API Machinery]