In the last couple of weeks, Amazon has changed the default placement of where Sponsored Products campaigns appear from on Amazon to 'Amazon and beyond' "sites".
"Sites are where specific ad placements can appear. These can be websites or apps.”
The two available Sites options are now "Amazon and beyond" or "Amazon Business".
So without any announcement, or ability to opt-out, all Sponsored Products campaigns have now been transitioned to 'Amazon and beyond' and your ad budget is being spent (at the same bids) on random websites and apps.
There is currently no report available to see where your ads are now appearing, or even what the potential list of websites and apps are where ads could show.
There is no ability to opt-out, and when you create a new campaign you also only have these two options.
If you've noticed your ACOS suddenly increase, this is very likely the reason why.
Even for Amazon this is a new low, with no transparency or ability to opt-out. You're now paying for ads on some random website or app, with likely no intent, at the same cost. Shocking levels of deception.
