qutebrowser is an open source keyboard-focused browser with a minimal GUI. Starting with qutebrowser v1.7.0, the Windows installer for qutebrowser registers a `qutebrowserurl:` URL handler. With certain applications, opening a specially crafted `qutebrowserurl:...` URL can lead to execution of qutebrowser commands, which in turn allows arbitrary code execution via commands such as `:spawn` or `:debug-pyeval`. Only Windows installs where qutebrowser is registered as URL handler are affected. The issue has been fixed in qutebrowser v2.4.0. The fix also adds additional hardening for potential similar issues on Linux (by adding the new --untrusted-args flag to the .desktop file), though no such vulnerabilities are known.

In qutebrowser versions less than 1.11.1, reloading a page with certificate errors shows a green URL. After a certificate error was overridden by the user, qutebrowser displays the URL as yellow (colors.statusbar.url.warn.fg). However, when the affected website was subsequently loaded again, the URL was mistakenly displayed as green (colors.statusbar.url.success_https). While the user already has seen a certificate error prompt at this point (or set content.ssl_strict to false, which is not recommended), this could still provide a false sense of security. This has been fixed in 1.11.1 and 1.12.0. All versions of qutebrowser are believed to be affected, though versions before v0.11.x couldn't be tested. Backported patches for older versions (greater than or equal to 1.4.0 and less than or equal to 1.10.2) are available, but no further releases are planned.

qutebrowser before version 1.4.1 is vulnerable to a cross-site request forgery flaw that allows websites to access 'qute://*' URLs. A malicious website could exploit this to load a 'qute://settings/set' URL, which then sets 'editor.command' to a bash script, resulting in arbitrary code execution.