In Splunk Enterprise 9.0 versions before 9.0.4, a View allows for Cross-Site Scripting (XSS) through the error message in a Base64-encoded image. The vulnerability affects instances with Splunk Web enabled. It does not affect Splunk Enterprise versions below 9.0.
https://research.splunk.com/application/ce6e1268-e01c-4df2-a617-0f034ed49a43/