Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHostnames" option when the "allowIframeRelativeUrls" is set to true, which allows attackers to bypass hostname whitelist for iframe element, related using an src value that starts with "/\\example.com". Reference: https://github.com/apostrophecms/sanitize-html/pull/460
This issue has been addressed in the following products: Red Hat OpenShift Container Platform 4.8 Via RHSA-2021:2438 https://access.redhat.com/errata/RHSA-2021:2438
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2021-26540
This issue has been addressed in the following products: Red Hat OpenShift Container Platform 4.9 Via RHSA-2021:3759 https://access.redhat.com/errata/RHSA-2021:3759