A malicious host header in an incoming HTTP request could cause NiFi to load resources from an external server. The fix to sanitize host headers and compare to a controlled whitelist was applied on the Apache NiFi 1.5.0 release. Users running a prior 1.x release should upgrade to the appropriate release.
In Apache NiFi before 1.0.1 and 1.1.x before 1.1.1, there is a cross-site scripting vulnerability in connection details dialog when accessed by an authorized user. The user supplied text was not being properly handled when added to the DOM.
In Apache NiFi before 0.7.4 and 1.x before 1.3.0, there are certain user input components in the UI which had been guarding for some forms of XSS issues but were insufficient.