How to reuse PIN codes in the most secure way?

https://security.stackexchange.com/questions/269321/how-to-reuse-pin-codes-in-the-most-secure-way

#passwordmanagement #credentialreuse #authentication #passwords

When you attempt to login on a website and it confirms that the email IS registered. I’ve heard that sites SHOULDN’T do that because it’s a security risk. How? How does knowing that X email is registered present a security risk? Is it due to the potential for credential stuffing / reuse attacks on that site or just user profile (I know Adam has an account at X)? #security #credentialreuse #credentialstuffing