Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
A jQuery cross site scripting vulnerability is present when making Ajax requests to untrusted domains. This vulnerability is mitigated by the fact that it requires contributed or custom modules in order to exploit. For Drupal 8, this vulnerability was already fixed in Drupal 8.4.0 in the Drupal core upgrade to jQuery 3. For Drupal 7, it is fixed in the current release (Drupal 7.57) for jQuery 1.4.4 (the version that ships with Drupal 7 core) as well as for other newer versions of jQuery that might be used on the site, for example using the jQuery Update module.
CWE-79 - Cross Site Scripting
Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.