There is a stored cross site scripting issue in Esri Portal for ArcGIS versions 11.5 and prior...

There is a stored cross site scripting issue in Esri Portal for ArcGIS versions 11.5 and prior that may allow a remote, administratively privileged attacker to inject malicious code that could potentially execute arbitrary in a victim’s browser. Users working with ArcGIS Enterprise 11.1, 11.3, and 11.5 are encouraged to patch. All users are advised to upgrade to the latest long-term support release.