- Added reconstruction of SELinux mount context after kubelet restart. Feature `SELinuxMountReadWriteOncePod` is now fully implemented and kubelet does not lose its cache of SELinux contexts after kubelet process restart. ([#113596](https://github.com/kubernetes/kubernetes/pull/113596), [@jsafrane](https://github.com/jsafrane))

* kube-apiserver: the OpenID Connect authenticator can now verify ID Tokens signed with JOSE algorithms other than RS256 through the --oidc-signing-algs flag. ([#58544](https://github.com/kubernetes/kubernetes/pull/58544), [@ericchiang](https://github.com/ericchiang))

- Fixes a regression in v1beta1 PodDisruptionBudget handling of `strategic merge patch`-type API requests for the `selector` field. Prior to 1.21, these requests would merge `matchLabels` content and replace `matchExpressions` content. In 1.21, patch requests touching the `selector` field started replacing the entire selector. This is consistent with server-side apply and the v1 PodDisruptionBudget behavior, but should not have been changed for v1beta1. ([#...

    url = ""
    content_type_level = "0"
    if override1:
        url += "/level1"
        content_type_level = "1"
    if override2:
        url += "/level2"
        content_type_level = "2"
    if override3:
        url += "/level3"
        content_type_level = "3"
    if override4:
        url += "/level4"
        content_type_level = "4"
    if override5:

### API Change

*   `conversion-gen` is now usable in a context without a vendored k8s.io/kubernetes. The Kubernetes core API is removed from `default extra-peer-dirs`. ([#54394](https://github.com/kubernetes/kubernetes/pull/54394),[ @sttts](https://github.com/sttts))

### API Change

- Ignore context canceled from validate and mutate webhook ([#120017](https://github.com/kubernetes/kubernetes/pull/120017), [@divyasri537](https://github.com/divyasri537)) [SIG API Machinery]

Certificate management has become more robust in 1.15, with kubeadm now seamlessly rotating all your certificates (on upgrades) before they expire. Check the [kubeadm documentation](https://github.com/kubernetes/website/blob/dev-1.15/content/en/docs/reference/setup-tools/kubeadm/kubeadm-alpha.md) for information on how to manage your certificates.

The kubeadm configuration file API is moving from v1beta1 to v1beta2 in 1.15.

    - [Client Binaries](#client-binaries-12)
    - [Server Binaries](#server-binaries-12)
    - [Node Binaries](#node-binaries-12)
- [Kubernetes 1.13 Release Notes](#kubernetes-113-release-notes)
  - [Security Content](#security-content)
  - [Urgent Upgrade Notes](#urgent-upgrade-notes)
    - [(No, really, you MUST do this before you upgrade)](#no-really-you-must-do-this-before-you-upgrade)
  - [Known Issues](#known-issues)