CVE-2024-3996 is a stored Cross-Site Scripting (XSS) vulnerability identified in the Smart Post Show WordPress plugin versions prior to 2.4.28. This vulnerability arises because the plugin fails to properly sanitize and escape certain settings inputs. Specifically, even high privilege users such as administrators can inject malicious scripts into the plugin's settings fields. Notably, this exploit is possible 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 vulnerability is classified under CWE-79, indicating improper neutralization of input during web page generation. The CVSS 3.1 base score is 6.1 (medium severity), with vector AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N, meaning the attack can be executed remotely over the network with low attack complexity, requires no privileges but does require user interaction, affects confidentiality and integrity with a scope change, but does not impact availability. The vulnerability allows an attacker to store malicious JavaScript code that executes in the context of users who view the affected pages, potentially leading to session hijacking, privilege escalation, or other malicious actions. Currently, there are no known exploits in the wild and no official patches linked, but the issue is publicly disclosed and tracked by WPScan and CISA. The affected product is a WordPress plugin used to display posts in a customizable manner, which is popular among WordPress site administrators for content presentation.

For European organizations using WordPress sites with the Smart Post Show plugin, this vulnerability poses a risk of persistent XSS attacks that can compromise site administrators and other users who access affected pages. The exploitation could lead to theft of authentication cookies, unauthorized actions performed with elevated privileges, or injection of malicious content that damages organizational reputation. In multisite WordPress setups common in enterprise environments, the risk is heightened because the vulnerability bypasses the usual 'unfiltered_html' restriction, potentially allowing attackers to inject scripts even in more restricted contexts. This can lead to lateral movement within the network if attackers leverage compromised credentials or sessions. The confidentiality and integrity of data managed through the WordPress site could be undermined, affecting customer data, internal communications, or content integrity. While availability is not directly impacted, the indirect effects of compromised administrative accounts could lead to site defacement or downtime. Given the widespread use of WordPress across European businesses, especially in sectors like media, education, and e-commerce, the threat could have broad implications if exploited.

Organizations should immediately verify if the Smart Post Show plugin is installed on their WordPress sites and identify the version in use. If the version is prior to 2.4.28, they should upgrade to the latest patched version as soon as it becomes available. In the absence of an official patch, administrators should consider temporarily disabling the plugin or restricting access to its settings pages to only the most trusted users. Implementing a Web Application Firewall (WAF) with custom rules to detect and block suspicious script injection attempts targeting the plugin's settings fields can provide interim protection. Additionally, reviewing and tightening user roles and capabilities to minimize the number of users with administrative privileges reduces the attack surface. Regular security audits and scanning for XSS payloads in plugin settings and site content can help detect exploitation attempts. Enabling Content Security Policy (CSP) headers to restrict the execution of inline scripts and untrusted sources can mitigate the impact of any injected scripts. Finally, educating site administrators about the risks of stored XSS and safe plugin management practices is essential.