Problem: The regex that validates smart proxies URLs only matches 'beginning of text'. This allows us to add just \n after a valid URL and put anything after it. For instance, javascript:alert('hacked'). I haven't found any link to the Foreman proxy URL so the script would not trigger, but if we were to put link_to @smart_proxy.url somewhere (or a plugin did this) it would be unsafe.

Solution: Make the regex match the end of the URL with \Z