Matthias,

> On Dec 23, 2025, at 9:29 AM, Matthias Fulz <[email protected]> 
> wrote:
> 
> Yes and THAT IS THE PROBLEM: OAuth SHOULD take CARE about! It's the core 
> protocol and it totally ignores the Identity Owner itself in the whole trust 
> model.

The IETF does not police implementations of its protocols.

OAuth best practices cover how to securely implement the OAuth protocol but 
does not mandate specific identifiers or kinds of identity validation - that is 
up to the AS implementation/configuration.  In fact, an identity might not even 
be a person.

If Facebook did not verify that you had access to the email account you supply 
as an identifier, that would be a clear security issue *in that implementation* 
and would likely have prevented that service from growing to its present size 
because users would not accept that impersonators could so easily hijack their 
email address.  However, that is *not* the case, FB *does* validate you have 
control of the email address you use, and in fact they also validate your real 
name in some situations - my FB "real name" is not my real name since 
apparently one of us Michael Sweet's is famous/well-known and I didn't/don't 
trust FB enough to send them a picture of gov't ID to verify my real name...  
Similarly, if you want to add your phone number(s) to your FB account, you have 
to verify you have access to those numbers.

Regardless of whether you use OAuth or some other scheme, the authorizing party 
is responsible for verifying your identity and establishing some way to 
validate access in the future, and *you* (the user) are responsible for 
trusting the authorizing party with your information to whatever extent you are 
comfortable.  For me and Facebook, I was OK supplying a throw-away email 
address that I have access to and a pseudonym that is close enough to my real 
name to allow friends and family to find/contact me there.  But they don't have 
my real name, address, phone number, or other email addresses that I use for 
different purposes.

________________________
Michael Sweet

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