Yes, it is in the docs:
https://docs.splunk.com/Documentation/Splunk/latest/Admin/Webconf
enable_insecure_login = <boolean>
* Whether or not the GET-based "/account/insecurelogin" REST endpoint is enabled.
* Provides an alternate GET-based authentication mechanism.
* If "true", the following url is available:
http://localhost:8000/en-US/account/insecurelogin?loginType=splunk&username=noc&password=XXXXXXX
* If "false", only the main /account/login endpoint is available
* Default: false
... View more