In Splunk SOAR versions below 8.7.0, an unauthenticated user with access to encrypted credential data from an affected Splunk SOAR instance could submit Basic authentication data to the Representational State Transfer (REST) API to expose and decrypt that encrypted credential data.
The vulnerability is possible because Splunk SOAR decrypts encrypted Basic authentication values before completing authentication checks.
The attack requires the unauthenticated user to have encrypted credential data from an affected Splunk SOAR instance. The unauthenticated user should not be able to exploit the vulnerability at will.
For more information see Using the REST API reference for Splunk SOAR (On-premises) (https://help.splunk.com/en/splunk-soar/soar-on-premises/rest-api-reference/8.5.0/using-the-splunk-soar-rest-api/using-the-rest-api-reference-for-splunk-soar-on-premises) in the Splunk documentation.