This could prove to be bit embarrassing for Yahoo if these allegations turn out to be true. The guy seems to have done his homework though.
Attackers who inject their banners onto reputable sites usually take advantage of the highly decentralized way that online advertisements are sold. It's not unusual for there to be a succession of affiliates, making it possible for an attacker to pose as an authorized agent of a name-brand product or service.
[H]ard|OCP - www.hardocp.com
[H]ard|OCP - www.hardocp.com
