### Immutable Secrets and ConfigMaps (beta)

Secret and ConfigMap volumes can be marked as immutable, which significantly reduces load on the API server if there are many Secret and ConfigMap volumes in the cluster.
See [ConfigMap](https://kubernetes.io/docs/concepts/configuration/configmap/) and [Secret](https://kubernetes.io/docs/concepts/configuration/secret/) for more information.

By default, the `fsgroup` setting, if specified, recursively updates permissions for every file in a volume on every mount. This can make mount, and pod startup, very slow if the volume has many files. 

Kubernetes 1.15 consists of **25 enhancements**: 2 moving to stable, 13 in beta, and 10 in alpha. The main themes of this release are:

#### Continuous Improvement
- Project sustainability is not just about features. Many SIGs have been working on  improving test coverage, ensuring the basics stay reliable, and stability of the core feature set and working on maturing existing features and cleaning up the backlog.

#### Extensibility

1A9A..1A9F    ; disallowed                             # NA   <reserved-1A9A>..<reserved-1A9F>
1AA0..1AA6    ; valid                  ;      ; NV8    # 5.2  TAI THAM SIGN WIANG..TAI THAM SIGN REVERSED ROTATED RANA
1AA7          ; valid                                  # 5.2  TAI THAM SIGN MAI YAMOK
1AA8..1AAD    ; valid                  ;      ; NV8    # 5.2  TAI THAM SIGN KAAN..TAI THAM SIGN CAANG

* ⬆️ Upgrade Starlette to 0.25.0. PR [#5996](https://github.com/tiangolo/fastapi/pull/5996) by [@tiangolo](https://github.com/tiangolo).
    * This solves a vulnerability that could allow denial of service attacks by using many small multipart fields/files (parts), consuming high CPU and memory.
    * Only applications using forms (e.g. file uploads) could be affected.
    * For most cases, upgrading won't have any breaking changes.

## 0.91.0

<pre>
'a'
'ä'
'本'
'\t'
'\000'
'\007'
'\377'
'\x07'
'\xff'
'\u12e4'
'\U00101234'
'\''         // rune literal containing single quote character
'aa'         // illegal: too many characters
'\k'         // illegal: k is not recognized after a backslash
'\xa'        // illegal: too few hexadecimal digits
'\0'         // illegal: too few octal digits
'\400'       // illegal: octal value over 255

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