I can see your local web servers

Nope, you can't

    Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost/. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing)

Anyway

    TypeError: /(192\.168\.[0-9]+\.)[0-9]+/.exec(...) is null i-can-see-your-local-web-servers:169:41

The Cross-Origin check be circumvented via DNS Rebinding: When you request mypage.com, my DNS returns the ip of my webserver. On all subsequent requests, it will return 127.0.0.1. Now localhost is on the same origin as my page.

It doesn't matter, you should be in control of a DNS the user relies on and you should have your server send

    Access-Control-Allow-Origin: mypage.com

or

    Access-Control-Allow-Origin: * 

which is not a default anywhere AFAIK and is domain based, not IP based

And your server should be enabled to respond to mypage.com host header

Based on m12k's suggested interpretation of your comment:

> you should be in control of a DNS the user relies on

You always are when a users visits your domain – you control the DNS of your domain.

> Access-Control-Allow-Origin: *

You don't need access-control headers, because you stay on the same domain.

> Your server should be enabled to respond to mypage.com host header

Most servers listening on localhost ignore the host header.

> You always are when a users visits your domain – you control the DNS of your domain.

I meant you need to control the poisoned DNS

If I use 8.8.8.8 as DNS you can only work on the domains you already control, which is kinda useless

> You don't need access-control headers, because you stay on the same domain.

No, you don't

My localhost server only respond to localhost and 127.0.0.1 host header

Not to mypage.com

Nginx does taht too by default

https://github.com/nginx/nginx/blob/master/conf/nginx.conf#L...

But even if you did, you still haven't resolved the issue: you can't make a call to a different domain without access-control headers, unless it's the same domain

you can't load mypage.com and then fetch from www.mypage.com, even if you resolve www.mypage.com to 127.0.0.1 the browser won't let you do it

> But even if you did, you still haven't resolved the issue: you can't make a call to a different domain without access-control headers, unless it's the same domain

> you can't load mypage.com and then fetch from www.mypage.com, even if you resolve www.mypage.com to 127.0.0.1 the browser won't let you do it

In this part you’re confusing what a rebinding attack is: by serving a DNS response with a short TTL an attacker is able to associate two different IPs to the same query, thus it'd be mypage.com and mypage.com (not www.mypage.com).. bypassing the same origin restrictions of the browsers.

https://capec.mitre.org/data/definitions/275.html