CVE-2021-26540: Apostrophecms Sanitize-Html

Medium severity, CVSS 5.3. EPSS: 1.8% chance of exploitation in the next 30 days.

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".

Affected products

• Apostrophecms Sanitize-Html: before 2.3.2 (fixed in 2.3.2)

Published 2021-02-08. Last modified 2026-06-17.