Which ecosystem feature used in Vault allows secure versioning of secrets?

The correct answer is that Key/Value versioning in Vault is the feature that enables secure versioning of secrets. This feature allows users to store and retrieve secrets in a way that maintains a history of changes made to those secrets, essentially allowing for the management of multiple versions. With Key/Value versioning, when updates are made to a secret, Vault creates a new version of that secret while retaining the previous versions. This capability is crucial for applications that require not only the ability to retrieve the current secret value but also to rollback to earlier versions if necessary, fostering both security and flexibility in secret management.

In contrast, Access Control Lists are primarily used to define permissions for users and applications, regulating who can access secrets, but do not inherently provide version control. Secret Engines in Vault serve as plugins that enable the storage and access of secrets but do not specifically focus on versioning. Token Policies govern the permissions of tokens issued in Vault, again not directly related to the versioning of secrets. Thus, Key/Value versioning stands out as the feature specifically designed to facilitate secure versioning of secrets in Vault.