On checking with our malware team, I’ve learnt that the domain: dentsu360 .com is on Google's "unsafe to advertise" list. This domain is flagged for incorporating varying DNS/IP while the creative is rendered; and from a user’s safety perspective, this is a security concern and unwanted. In this situation, the client would have to host the creative in a different server/domain in order to get this cleaned.
Should you have any questions, do write back and I’ll be happy to assist you in the best way possible.