The Splunk Enterprise REST API allows enumeration of usernames via the lockout error message. The potential vulnerability impacts Splunk Enterprise instances before 8.1.7 when configured to repress verbose login errors.
https://www.splunk.com/en_us/product-security/announcements/svd-2022-0502.html
https://research.splunk.com/application/splunk_user_enumeration_attempt/