A bevy of big Madison Avenue media-buying agencies took aim at a seven-month probe conducted by the Association of National Advertisers suggesting the acceptance of rebates and other forms of kickbacks are “pervasive” among a cadre of ad firms that handle billions of promotional dollars for products ranging from Apple to Zyrtec.

Among the allegations contained in the report released Tuesday are suggestions that big ad buyers accept cash and ad inventory from vendors in exchange for committing a greater volume of ad dollars to them. In some cases, the report alleged, the media buying firms might buy the inventory at one price, then sell it to their clients at a higher cost.

Read the full Variety article here.