When updating a Process Group via the API in NiFi versions 1.3.0 to 1.9.2, the response to the request includes all of its contents (at the top most level, not recursively). The response included details about processors and controller services which the user may not have had read access to.

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.

An authorized user could upload a template which contained malicious code and accessed sensitive files via an XML External Entity (XXE) attack. The fix to properly handle XML External Entities was applied on the Apache NiFi 1.4.0 release. Users running a prior 1.x release should upgrade to the appropriate release.