wp_kses_bad_protocol in wp-includes/kses.php in WordPress before 5.3.1 mishandles the HTML5 colon named entity, allowing attackers to bypass input sanitization, as demonstrated by the javascript: substring.
https://www.debian.org/security/2020/dsa-4677
https://www.debian.org/security/2020/dsa-4599
https://seclists.org/bugtraq/2020/Jan/8
https://lists.debian.org/debian-lts-announce/2020/01/msg00010.html
https://wordpress.org/news/2019/12/wordpress-5-3-1-security-and-maintenance-release/
https://github.com/WordPress/wordpress-develop/commit/b1975463dd995da19bb40d3fa0786498717e3c53
Source: Mitre, NVD
Published: 2019-12-27
Updated: 2022-11-23
Base Score: 7.5
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P
Severity: High
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity: Critical
EPSS: 0.03102