The vulnerability can be exploited by loading an HTML page that uses specially crafted CSS code. The CSS code isn't very complex and tries to apply a CSS effect known as backdrop-filter to a ...

Use this handy, simplified guide to quickly learn HTML and CSS -- a foundation of modern web development.

Tony Patton focuses on CSS fundamentals and explains how multiple rules for the same element are handled. Multiple rules ensure that there will be no surprises for either you or the user community.