Safari PoC: SetCookie via intermediate 3rd-party iframe

How to use

Create a host entry in /etc/hosts:

127.0.0.1   ad

Start servers:

php -S localhost:2001 root.php
php -S localhost:2002 ad.php

Open localhost:2001.

Refresh the page once.

Firefox and Chrome will display a different output than Safari, because Firefox and Chrome do not allow setting a SameSite=Lax-cookie via an intermediate 3rd-party iframe.

Chrome blocks cookies from same-site when loaded via 3rd-party frame

Also true for Firefox.

Safari allows cookies from same-site when loaded via 3rd-party frame