Bypass Google Open Redirect Filter Based on Google
Bypass Google Open Redirect Filter Based on Googleads.g.doubleclick.net
However, if the URLs in a redirected domain have open URL redirection
vulnerabilities themselves, a user could be redirected from Google to a
vulnerable URL in that domain first and later be redirected from this
vulnerable site to a malicious site. This is as if being redirected from
Google directly.
https://seclists.org/fulldisclosure/2014/Nov/37