XSS can occur in GNOME Web (aka Epiphany) before 40.4 and 41.x before 41.1 via an about: page, as demonstrated by ephy-about:overview when a user visits an XSS payload page often enough to place that page on the Most Visited list.
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2021-45085.json"