Another reason why "web security" is the most immensely depressing topic in modern computing.
It turns out you can't actually achieve a simple, secure system by repeatedly rushing to fix problems as they arise.
It turns out you can't actually achieve a simple, secure system by repeatedly rushing to fix problems as they arise.
Everything has to be same origin. Exceptions only to be allowed with case-by-case explicit consent of the user.
The only thing that should bridge one website to another is a link to the 'top' level document.