Is it possible to publicly document third party web applications?

Question

Documentation

Is it possible to document, for example, a description of REST requests used in a personal account or mobile application of a store/bank/financial organization in the public space of the Internet?

For example, when I log into the personal account of "Store A" (or "Bank A", etc.), I see a POST /login request, Request "login":"mySecretLogin", etc. - and I want to parse the passed and returned parameters, I want to write this on my blog. This information is available in the browser's debugger...

PS Why? Sometimes interesting things come up - for example, the category of the client or other flags, etc. Plus - then use as a portfolio analytics of Internet and mobile applications.

Answer 1

judging by the closure of mgp25 by DMCA, they don’t really like it, they pull up that the site is not your product and not your property,
but of course, in streamlined versions, it’s possible,
but why?

Answer 2

For reversing the site of a bank or other financial organization, they can easily and naturally pull up when this site is hacked. Do not joke with banks, it is fraught.