In wp-includes/formatting.php in WordPress 3.7 to 5.3.0, the function wp_targeted_link_rel() can be used in a particular way to result in a stored cross-site scripting (XSS) vulnerability. This has been patched in WordPress 5.3.1, along with all the previous WordPress versions from 3.7 to 5.3 via a minor release.
Created wordpress tracking bugs for this issue:
Affects: epel-6 [bug 1793616]
Affects: epel-7 [bug 1793617]