In Epiphany (aka GNOME Web) through 43.0, untrusted web content can trick users into exfiltrating passwords, because autofill occurs in sandboxed contexts.

In GNOME Epiphany before 41.4 and 42.x before 42.2, an HTML document can trigger a client buffer overflow (in ephy_string_shorten in the UI process) via a long page title. The issue occurs because the number of bytes for a UTF-8 ellipsis character is not properly considered.

XSS can occur in GNOME Web (aka Epiphany) before 40.4 and 41.x before 41.1 via an error page.

XSS can occur in GNOME Web (aka Epiphany) before 40.4 and 41.x before 41.1 when View Source mode or Reader mode is used, as demonstrated by a a page title.

XSS can occur in GNOME Web (aka Epiphany) before 40.4 and 41.x before 41.1 because a server's suggested_filename is used as the pdf_name value in PDF.js.

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.

WebKitGTK and WPE WebKit prior to version 2.24.1 are vulnerable to address bar spoofing upon certain JavaScript redirections. An attacker could cause malicious web content to be displayed as if for a trusted URI. This is similar to the CVE-2018-8383 issue in Microsoft Edge.

libephymain.so in GNOME Web (aka Epiphany) through 3.28.2.1 allows remote attackers to cause a denial of service (application crash) via certain window.open and document.write calls.

ephy-session.c in libephymain.so in GNOME Web (aka Epiphany) through 3.28.2.1 allows remote attackers to cause a denial of service (application crash) via JavaScript code that triggers access to a NULL URL, as demonstrated by a crafted window.open call.

The International Domain Name (IDN) support in Epiphany allows remote attackers to spoof domain names using punycode encoded domain names that are decoded in URLs and SSL certificates in a way that uses homograph characters from other character sets, which facilitates phishing attacks.