Improper Restriction of XML External Entity Reference
The XMLFileLookupService in NiFi versions 1.3.0 to 1.9.2 allowed trusted users to inadvertently configure a potentially malicious XML file. The XML file has the ability to make external calls to services (via XXE) and reveal information such as the versions of Java, Jersey, and Apache that the NiFI instance uses.
CWE-611 - Improper Restriction of XML External Entity Reference
Listed 4th in the 'OWASP Top Ten', XML External Entities (XXE) vulnerability allows attackers to provide an XML input that contains an external entity. When the XML is parsed, it can cause data extraction and manipulation, execution of commands, denial-of-service attacks, and server-side request forgery.