DEF CON 30 - Dongsung Kim - CSRF Resurrections Starring the Unholy Trinity

CSRF is (really) dead. SameSite killed it. Browsers protect us. Lax by default! Sounds a bit too good to be true, doesn't it? We live in a world where browsers get constantly updated with brand new web features and new specifications. The complexity abyss is getting wider and deeper. How do we know web technologies always play perfectly nice with each other? What happens when something slips? In this talk, I focus on three intertwined web features: HTTP Cookie's SameSite attribute, PWA's Service Worker, and Fetch. I will start by taking a look at how each feature works in detail. Then, I will present how the three combined together allows CSRF to be resurrected, bypassing the SameSite's defense. Also, I will demonstrate how a web developer can easily introduce the vulnerability to their web apps when utilizing popular libraries. I will end the talk by sharing the complex disclosure timeline and the difficulty of patching the vulnerability due to the interconnected nature of web specifications.