CVE-2023-5956 is a medium severity stored Cross-Site Scripting (XSS) vulnerability affecting the WordPress plugin Wp-Adv-Quiz up to version 1.0.2. The vulnerability arises because the plugin fails to properly sanitize and escape certain settings inputs. This flaw allows users with high privileges, such as administrators, to inject malicious scripts that are stored persistently within the plugin's settings. Notably, this vulnerability can be exploited even when the WordPress capability 'unfiltered_html' is disabled, such as in multisite environments, which typically restricts the ability to post unfiltered HTML content. The attack vector requires network access (remote), low attack complexity, and high privileges, with user interaction needed to trigger the malicious payload. The vulnerability impacts confidentiality and integrity by enabling script injection that could lead to session hijacking, privilege escalation, or unauthorized actions performed in the context of an admin user. However, it does not affect availability. No known public exploits have been reported yet, and no patches are currently linked, indicating that mitigation may require manual intervention or plugin updates once available. The CVSS 3.1 base score is 4.8, reflecting a medium severity rating. The vulnerability is classified under CWE-79, which covers improper neutralization of input during web page generation leading to XSS.

For European organizations using WordPress sites with the Wp-Adv-Quiz plugin, this vulnerability poses a risk primarily to the confidentiality and integrity of their web applications. An attacker with admin-level access could inject malicious scripts that execute in the browsers of other administrators or privileged users, potentially leading to credential theft, session hijacking, or unauthorized administrative actions. This could result in data breaches, defacement, or further compromise of internal systems. In multisite WordPress deployments common in larger organizations or managed service providers, the risk is heightened because the usual safeguard of disabling 'unfiltered_html' does not prevent exploitation. Given the widespread use of WordPress across European businesses, educational institutions, and government websites, exploitation could disrupt trust and lead to regulatory consequences under GDPR if personal data is exposed. However, the requirement for high privileges to exploit limits the threat to insiders or attackers who have already compromised an admin account, reducing the likelihood of external exploitation without prior access.

European organizations should immediately audit their WordPress installations to identify the presence of the Wp-Adv-Quiz plugin and its version. Until an official patch is released, administrators should consider disabling or uninstalling the plugin if it is not essential. For sites requiring the plugin, restrict admin access strictly and monitor for unusual administrative activity. Implement Web Application Firewall (WAF) rules to detect and block suspicious payloads targeting plugin settings. Additionally, enforce strong authentication mechanisms such as multi-factor authentication (MFA) for all admin users to reduce the risk of credential compromise. Regularly review and sanitize all user inputs and plugin settings manually if possible. Organizations should subscribe to vulnerability feeds and update the plugin promptly once a patch is available. Finally, conduct security awareness training for administrators about the risks of stored XSS and safe plugin management practices.