In Splunk Enterprise versions below 9.2.1, 9.1.4, and 9.0.9, the software potentially exposes authentication tokens during the token validation process. This exposure happens when either Splunk Enterprise runs in debug mode or the JsonWebToken component has been configured to log its activity at the DEBUG logging level.
https://research.splunk.com/application/9a67e749-d291-40dd-8376-d422e7ecf8b5