- `LabelSelectors` specified in `topologySpreadConstraints` were validated to ensure that pods are scheduled as expected. Existing pods with invalid `LabelSelectors` could be updated, but new pods were required to specify valid `LabelSelectors`. ([#111802](https://github.com/kubernetes/kubernetes/pull/111802), [@maaoBit](https://github.com/maaoBit))

the incoming pod labels, those key-value labels are ANDed with labelSelector to select the group of existing pods over which spreading will be calculated for the incoming pod. The same key is forbidden to exist in both MatchLabelKeys and LabelSelector. MatchLabelKeys cannot be set when LabelSelector isn't set. Keys that don't exist in the incoming pod labels will be ignored. A null or empty list means only match against labelSelector.\n\nThis is a beta field and requires the MatchLabelKeysInPodTopologySpread...

- The Kubernetes apiserver now emits a warning message for Pods with a null labelSelector in podAffinity or topologySpreadConstraints. The null labelSelector means "match none". Using it in podAffinity or topologySpreadConstraint could lead to unintended behavior. ([#117025](https://github.com/kubernetes/kubernetes/pull/117025), [@sanposhiho](https://github.com/sanposhiho))...