* If the serialization type is 'application/json':
    * If serialization fails, and the original status code was an failure (e.g. 4xx or 5xx), the original status code will be returned.

* Protobuf serialization does not distinguish between `[]` and `null`. ([#45294](https://github.com/kubernetes/kubernetes/pull/45294), [@liggitt](https://github.com/liggitt))

* Protobuf serialization does not distinguish between `[]` and `null`. ([#45294](https://github.com/kubernetes/kubernetes/pull/45294), [@liggitt](https://github.com/liggitt))

## Changes by Kind

### API Change

- Protobuf serialization of metav1.MicroTime timestamps (used in `Lease` and `Event` API objects) has been corrected to truncate to microsecond precision, to match the documented behavior and JSON/YAML serialization. Any existing persisted data is truncated to microsecond when read from etcd. ([#111936](https://github.com/kubernetes/kubernetes/pull/111936), [@h...

* Fix issue in reconstruct volume data when kubelet restarts ([#36616](https://github.com/kubernetes/kubernetes/pull/36616), [@jingxu97](https://github.com/jingxu97))
* Ensure proper serialization of updates and creates in federation test watcher ([#36613](https://github.com/kubernetes/kubernetes/pull/36613), [@mwielgus](https://github.com/mwielgus))

request contained label or field selectors, then the number of remaining items is unknown and the field will be left unset and omitted during serialization. If the list is complete (either because it is not chunking or because this is the last chunk), then there are no more remaining items and this field will be left unset and omitted during serialization. Servers older than v1.15 do not set this field. The intended use of the remainingItemCount is *estimating* the size of a collection. Clients should...

## Changes by Kind

### API Change

* Protobuf serialization does not distinguish between `[]` and `null`.
API fields previously capable of storing and returning either `[]` and `null` via JSON API requests (for example, the Endpoints `subsets` field)
can now store only `null` when created using the protobuf content-type or stored in etcd using protobuf serialization (the default in 1.6).

   ([#122292](https://github.com/kubernetes/kubernetes/pull/122292), [@sanposhiho](https://github.com/sanposhiho))
- 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))