User enumeration can occur in the Authentication REST API in Delinea PAM Secret Server 11.4. This allows a remote attacker to determine whether a user is valid because of a difference in responses from the /oauth2/token endpoint.
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.