wp-includes/functions.php in WordPress before 4.9.1 does not require the unfiltered_html capability for upload of .js files, which might allow remote attackers to conduct XSS attacks via a crafted file.
https://www.debian.org/security/2018/dsa-4090
https://wpvulndb.com/vulnerabilities/8966
https://wordpress.org/news/2017/11/wordpress-4-9-1-security-and-maintenance-release/
https://lists.debian.org/debian-lts-announce/2017/12/msg00019.html
https://github.com/WordPress/WordPress/commit/67d03a98c2cae5f41843c897f206adde299b0509