wp-includes/feed.php in WordPress before 4.9.1 does not properly restrict enclosures in RSS and Atom fields, which might allow attackers to conduct XSS attacks via a crafted URL.
www.securityfocus.com/bid/102024
codex.wordpress.org/Version_4.9.1
github.com/WordPress/WordPress/commit/f1de7e42df29395c3314bf85bff3d1f4f90541de
lists.debian.org/debian-lts-announce/2017/12/msg00019.html
wordpress.org/news/2017/11/wordpress-4-9-1-security-and-maintenance-release/
wpvulndb.com/vulnerabilities/8967
www.debian.org/security/2018/dsa-4090