In Splunk Enterprise versions below 9.0.7 and 9.1.2, Splunk Enterprise does not safely sanitize extensible stylesheet language transformations (XSLT) that users supply. This means that an attacker can upload malicious XSLT which can result in remote code execution on the Splunk Enterprise instance.
https://research.splunk.com/application/a053e6a6-2146-483a-9798-2d43652f3299/
https://research.splunk.com/application/6cb7e011-55fb-48e3-a98d-164fa854e37e/