There is a Cross-site Scripting vulnerability in Portal for ArcGIS in versions 11.1 and below that may allow a remote, authenticated attacker to create a crafted link which when opening an authenticated users bio page will render an image in the victims browser. The privileges required to execute this attack are low.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.