How to safely transfer information from one site to cookies of another?

Question

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Good day!

Please, tell me how to solve the problem?

There are two different sites ("A" and "B") on different domains. On site "A", the user selects the product he wants to purchase.
After choosing a product, he clicks "checkout" - and he will be redirected to site "B", where he is already paying for the goods. When switching from "A" to "B", only the name of the product, price and quantity are transmitted.
There is an authorization on the site "B", so the product data must be stored (in cookies?) for a while until the user logs in.
What solutions can you offer?
Thanks in advance.

Answer 1

Unclear. This one, what is it?

Answer 2

generate a link to B in which all the necessary parameters, B receives them from there when loading the page and saves them where necessary (session on the server, cookies, localstorage)