Lots of existing apps, including some that handle payment information, rely on window.opener to provide a seamless experience when using pop-ups or iframes from a different domain.
In an ideal world, these apps would have been rewritten a long time ago using more modern techniques. In reality, browsers bend over backwards to maintain backward compatibility with existing apps.
In an ideal world, these apps would have been rewritten a long time ago using more modern techniques. In reality, browsers bend over backwards to maintain backward compatibility with existing apps.