This indicates an attack attempt to exploit a Information Disclosure vulnerability in Splunk Enterprise.
The vulnerability is due to an error when handling crafted HTTP reqeust. A remote attacker can exploit this vulnerability by sending crafted HTTP request. Successful exploitation could result in the disclosure of sensitive information which may be used to further compromise the target system.
Splunk Enterprise versions prior to 7.0.1
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.