The world of online ad buying can be pretty opaque. For many advertisers, the path an ad impression takes is murky—standard reports often don’t reveal which, or how many, exchanges and supply-side platforms (SSPs) handled the inventory along the way.

An ADWEEK investigation found that media buyers at WPP, IPG, Dentsu, Havas, several independents, and one Fortune 500 brand unknowingly bought ads through Publicis Groupe’s Epsilon SSP via reseller supply paths. So while they thought they were buying through a given SSP, like Magnite or PubMatic, the purchased inventory had passed through Epsilon SSP. This means that dollars and data were in some cases sent to Publicis, a direct competitor. 

Each resold impression not only adds fees but also exposes bidstream data to the SSP, revealing who the advertiser is, how much they’re bidding, what audiences they’re targeting, and more. Programmatic experts explained that such data could give Publicis valuable intel to win new business. Publicis denies using this data to gain a competitive advantage. 

In this episode of Adspeak, ADWEEK staffers are joined by Arielle Garcia, chief operating officer of adtech watchdog Check My Ads, and an anonymous media buyer. Together, they unpack how reselling works in the programmatic ecosystem, the story of how some advertisers learned they’d unknowingly bought ad space via Publicis’ Epsilon SSP, and why some are concerned that Publicis’ role in the industry constitutes a conflict of interest. 

Tune in now.