- Kube-apiserver: regular expressions specified with the `--cors-allowed-origins` option are now validated to match the entire `hostname` inside the `Origin` header of the request and 
  must contain '^' or the '//' prefix to anchor to the start, and '$' or the port separator ':' to anchor to 

### Bug or Regression

- Consider only plugin directory and not entire kubelet root when cleaning up mounts ([#112920](https://github.com/kubernetes/kubernetes/pull/112920), [@mattcary](https://github.com/mattcary)) [SIG Storage]

* If a required flag is not provided to a command, the user will only see the required flag error message, instead of the entire usage menu. ([#86693](https://github.com/kubernetes/kubernetes/pull/86693), [@sallyom](https://github.com/sallyom))

- Trace output in apiserver logs is more organized and comprehensive. Traces are nested, and for all non-long running request endpoints, the entire filter chain is instrumented (e.g. authentication check is included). ([#88936](https://github.com/kubernetes/kubernetes/pull/88936), [@jpbetz](https://github.com/jpbetz)) [SIG API Machinery, CLI, Cloud Provider, Cluster Lifecycle, Instrumentation...

"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. ([#108142](https://github.com/kubernetes/kubernetes/pull/108142), [@liggitt](https://github.com/liggitt)) [SIG...

### Bug or Regression

- Consider only plugin directory and not entire kubelet root when cleaning up mounts ([#112887](https://github.com/kubernetes/kubernetes/pull/112887), [@mattcary](https://github.com/mattcary)) [SIG Storage]

}\n\n      .order#{$infix}-last { order: $columns + 1; }\n\n      @for $i from 0 through $columns {\n        .order#{$infix}-#{$i} { order: $i; }\n      }\n\n      @if $columns > 0 {\n        // `$columns - 1` because offsetting by the width of an entire row isn't possible\n        @for $i from 0 through ($columns - 1) {\n          @if not ($infix == \"\" and $i == 0) { // Avoid emitting useless .offset-0\n            .offset#{$infix}-#{$i} {\n              @include make-col-offset($i, $columns);\n...

.order#{$infix}-first { order: -1; }\n\n      .order#{$infix}-last { order: $columns + 1; }\n\n      @for $i from 0 through $columns {\n        .order#{$infix}-#{$i} { order: $i; }\n      }\n\n      // `$columns - 1` because offsetting by the width of an entire row isn't possible\n      @for $i from 0 through ($columns - 1) {\n        @if not ($infix == \"\" and $i == 0) { // Avoid emitting useless .offset-0\n          .offset#{$infix}-#{$i} {\n            @include make-col-offset($i, $columns);\n      ...

}\n\n      .order#{$infix}-last { order: $columns + 1; }\n\n      @for $i from 0 through $columns {\n        .order#{$infix}-#{$i} { order: $i; }\n      }\n\n      @if $columns > 0 {\n        // `$columns - 1` because offsetting by the width of an entire row isn't possible\n        @for $i from 0 through ($columns - 1) {\n          @if not ($infix == \"\" and $i == 0) { // Avoid emitting useless .offset-0\n            .offset#{$infix}-#{$i} {\n              @include make-col-offset($i, $columns);\n...