The Browser Company of New York Dia vulnerabilities

Missing about:blank indicator in custom-sized new windows in Dia before 1.9.0 on macOS could allow an attacker to spoof a trusted domain in the window title and mislead users about the current site.

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.)