When you try to maximize ad revenue, you add multiple advertising SDKs to your website, each of which can often do live bidding with hundreds of ad/data brokers

You can usually check the ads.txt file on a website to see which companies are allowed to bid for ad space on there. For example, for dict.cc, the website in question:

https://dict.cc/ads.txt

The ones labelled "RESELLER" will probably share your data with even more ad companies.

How have I not heard about this. I am both impressed and horrified.