CVE-2024-4091 is a medium-severity Cross-Site Scripting (XSS) vulnerability identified in the Responsive Gallery Grid WordPress plugin versions prior to 2.3.15. This vulnerability arises because the plugin fails to properly sanitize and escape certain settings inputs. As a result, high-privilege users, such as administrators, can inject malicious scripts into the plugin's settings interface. Notably, this XSS can be exploited even when the WordPress 'unfiltered_html' capability is disabled, which normally restricts the ability to post unfiltered HTML content. The vulnerability is classified under CWE-79, indicating improper neutralization of input during web page generation. The CVSS 3.1 base score is 6.1, reflecting a medium severity level. The vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) indicates that the attack can be performed remotely over the network with low attack complexity, no privileges required, but requires user interaction (e.g., an administrator visiting a crafted page). The scope is changed, meaning the vulnerability affects resources beyond the initially vulnerable component. The impact affects confidentiality and integrity to a limited extent but does not affect availability. There are no known exploits in the wild at the time of publication, and no official patches or mitigation links have been provided yet. This vulnerability primarily targets WordPress sites using the Responsive Gallery Grid plugin, which is used to display image galleries responsively. Exploitation could allow attackers to execute arbitrary JavaScript in the context of the admin user, potentially leading to session hijacking, privilege escalation, or further compromise of the WordPress installation.

For European organizations, the impact of this vulnerability depends on the prevalence of the Responsive Gallery Grid plugin within their WordPress deployments. Organizations using this plugin with versions prior to 2.3.15 are at risk of targeted attacks that could compromise administrative accounts. Successful exploitation could lead to unauthorized disclosure of sensitive information (confidentiality impact) and unauthorized modification of site content or settings (integrity impact). Although availability is not directly affected, the indirect consequences of compromised admin accounts could include site defacement or insertion of malicious content affecting users and customers. Given that WordPress powers a significant portion of websites in Europe, including many small and medium enterprises, cultural institutions, and public sector websites, this vulnerability could be leveraged by attackers to gain footholds for further attacks or data theft. The requirement for user interaction and the need for an attacker to lure an admin to a malicious page somewhat limits the attack surface but does not eliminate risk, especially in environments where social engineering or phishing attacks are common. Additionally, the vulnerability could be exploited in targeted attacks against high-value European organizations that rely on WordPress for their web presence.

1. Immediate mitigation involves updating the Responsive Gallery Grid plugin to version 2.3.15 or later once available, as this will include proper sanitization and escaping of settings inputs. 2. Until an official patch is released, administrators should restrict access to the WordPress admin dashboard to trusted users only and consider implementing multi-factor authentication (MFA) to reduce the risk of compromised credentials. 3. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious input patterns related to XSS payloads targeting the plugin's settings. 4. Educate administrators and privileged users about phishing and social engineering risks to reduce the likelihood of them visiting malicious links that could trigger the XSS. 5. Regularly audit installed plugins and remove any that are unused or unsupported to minimize attack surface. 6. Monitor logs for unusual admin activity or unexpected changes in plugin settings that could indicate exploitation attempts. 7. Consider deploying Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the WordPress admin interface.