In October 2017, security researcher Mathy Vanhoef published a paper describing Key Reinstallation Attacks — KRACK — against the WPA2 four-way handshake. The disclosure triggered emergency patches across every major operating system, router firmware, and WiFi chipset vendor simultaneously. It was the most significant WiFi security event between WEP’s collapse in the early 2000s and WPA3’s introduction in 2018. Understanding what KRACK was, and what it actually threatened, clarifies both the state of WPA2 security today and how the WiFi security ecosystem responds to structural vulnerabilities.