Impact statement for the OCPBUGS-75916 series:

Which 4.y.z to 4.y'.z' updates increase vulnerability?

Any 4.20.z to 4.21.0 (and potentially 4.21.1 depending on fix timing in the OCPBUGS-75917 backport).

Which types of clusters?

Any cluster where customers are using unqualified search registries. Situations with many quay replicas are particularly risky targets, if the user didn't set up proper mirroring but instead is relying on ambiguous search paths.

What is the impact? Is it serious enough to warrant removing update recommendations?

Pods with images that use "short names" (image names with no domain specified) will fail to run.

How involved is remediation?

There is a way to turn off this behavior, but it's not convenient. Customers may also change the paths of their images to be more explicit (not exclude the domain name from the image name).

Is this a regression?

It's a security enhancement that can cause regressions. In some cases, the security risk (which is low) is worth the added behavior of having CRI-O iterate through the unqualified search registries until it finds the image it needs. Thus, it is a regression for users who rely on this behavior.