In Splunk Enterprise versions below 8.1.13, 8.2.10, and 9.0.4, the lookup table upload feature let a user upload lookup tables with unnecessary filename extensions. Lookup table file extensions may now be one of the following only: .csv, .csv.gz, .kmz, .kml, .mmdb, or .mmdb.gzl.
https://research.splunk.com/application/b7d1293f-e78f-415e-b5f6-443df3480082/