This vulnerability allowed a site to enter fullscreen, after a user click, without a full-screen notification (toast) appearing. Without this notification, users could potentially be misled about what site they were on if a malicious site renders a fake UI (like a fake address bar.)
Exploitability
AV:NAC:LPR:NUI:RScope
S:CImpact
C:NI:HA:N7.4/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:NOther