A flaw was found in Yelp due to an overly permissive Content Security Policy (CSP) implementation provided by yelp-xsl. A malicious Flatpak application can open crafted help content through the OpenURI portal. By embedding an untrusted CSS stylesheet within a structured SVG document, attacker-controlled content can bypass Flatpak's intended sandbox isolation, allowing Yelp to evaluate local XML inclusions and disclose arbitrary user-readable host files through remote CSS resource requests. This may result in the unauthorized disclosure of sensitive information.
https://gitlab.gnome.org/GNOME/yelp/-/work_items/238
https://blogs.gnome.org/mcatanzaro/2026/05/11/flatpak-sandbox-escape-via-yelp/
https://access.redhat.com/errata/RHSA-2026:54666
https://access.redhat.com/errata/RHSA-2026:54637
https://access.redhat.com/errata/RHSA-2026:54624
https://access.redhat.com/errata/RHSA-2026:54605
https://access.redhat.com/errata/RHSA-2026:54540
https://access.redhat.com/errata/RHSA-2026:54539