Reported by Tomer Brisker to foreman-security:

I have discovered a stored XSS vulnerability in the host and hostgroup edit forms caused by smart class parameters and smart variables.

These forms display a popover that shows additional info about any of the parameters that can be overridden. The popover is rendered with HTML but contains values that can be input by a user - the parameter description, and in develop branch also the inherited value.

Effectively, any user who can edit parameters can input arbitrary HTML or JS into the description field or the default value, which will be executed once the popover is triggered by any other user.

This affects all versions of Foreman.

CVE identifier is CVE-2015-7518.