Side channel attacks via CSS in FF and Chrome…

Side-channel attacking browsers through CSS3 features | Security Research – Evonide https://www.evonide.com/side-channel-attacking-browsers-through-css3-features/

With the staggering amount of features that were introduced through HTML5 and CSS3 the attack surface of browsers grew accordingly. Consequently, it is no surprise that interactions between such features can cause unexpected behavior impacting the security of their users. In this article, we describe such a practical attack and the research behind it.