Why does the browser send a request to clad.ld.yandex.ru when logging in to the Microsoft website?

Question

OAuth

Marvelous. In Ukraine, as you know, Yandex is blocked (it was thanks to this that I discovered this).
When you try to login to the visualstudio.com website and enter soap from yandex.ru in the email field (just an email, NOT authorization like Login under Facebook, etc.; there should not be any exchange of tokens with Yandex, I can enter any email there, not Yandex) the site accesses from my client (!!!) to https://clad.ld.yandex.ru
And here, of course, everything is blocked, so I can't log in.
1. Why does the Microsoft site contact Yandex and transfer my data?
2. How normal is it to access third domains without the knowledge of clients from their browser (after all, it is normal practice to do this through your own server, the same OAuth).

Answer 1

If you enter non-Yandex mail, it does not apply, you can simply enter ya.ru instead of yandex.ru, it will log in. Some bug in the new interface, apparently.
1. It looks like there is an attempt to authorize via Yandex or to call the validation of the mail name.
2. All sites access third-party domains from their browser without the knowledge of clients. From the CDN system to third-party analytics systems, where they don’t send anything about us. Technically, this is not considered personal data. If it is personal data that will be sent, then it is necessary to obtain your consent to the terms of their use.