CVE-2024-9663 is a medium-severity vulnerability identified in the CYAN Backup WordPress plugin versions prior to 2.5.3. The vulnerability is a Stored Cross-Site Scripting (XSS) issue categorized under CWE-79. It 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 into the plugin's stored settings. Notably, this vulnerability can be exploited even when the WordPress unfiltered_html capability is disabled, such as in multisite environments, which typically restricts the ability to post unfiltered HTML content. The CVSS 3.1 base score is 5.4, reflecting a medium severity level, with an attack vector of network (remote exploitation), low attack complexity, requiring privileges (PR:L), and user interaction (UI:R). The scope is changed (S:C), indicating that the vulnerability can affect resources beyond the initially vulnerable component. The impact affects confidentiality and integrity to a limited extent but does not affect availability. Exploitation would require an authenticated user with elevated privileges to perform actions that store malicious scripts, which could then execute in the context of other administrators or users viewing the affected settings. This could lead to session hijacking, privilege escalation, or other malicious activities within the WordPress administrative interface. No known exploits are currently reported in the wild, and no official patches or updates are linked yet, but upgrading to version 2.5.3 or later is implied to remediate the issue. The vulnerability is assigned by WPScan and enriched by CISA, indicating credible recognition in the security community.

For European organizations using WordPress sites with the CYAN Backup plugin, this vulnerability poses a risk primarily to the confidentiality and integrity of administrative sessions and data. If exploited, attackers with admin privileges could inject malicious scripts that execute in other administrators' browsers, potentially leading to credential theft, unauthorized actions, or further compromise of the WordPress environment. This could disrupt business operations, lead to data breaches, or damage organizational reputation. The risk is heightened in multisite WordPress installations common in larger enterprises or managed service providers, where the unfiltered_html capability is often disabled to restrict content injection, yet this vulnerability bypasses that safeguard. Given the widespread use of WordPress in Europe for corporate websites, e-commerce, and public sector portals, exploitation could impact sensitive data and critical services. However, the requirement for high privileges and user interaction limits the attack surface to insider threats or compromised admin accounts rather than external unauthenticated attackers. The absence of known active exploits reduces immediate risk but does not eliminate the need for proactive mitigation.

European organizations should immediately verify if their WordPress installations use the CYAN Backup plugin and identify the plugin version. If running a version prior to 2.5.3, they should prioritize upgrading to the latest version that addresses this vulnerability. In the absence of an official patch, organizations can implement temporary mitigations such as restricting administrative access to trusted personnel only, enforcing strong multi-factor authentication (MFA) for all admin accounts to reduce the risk of credential compromise, and monitoring for unusual administrative activity or unexpected changes in plugin settings. Additionally, applying Web Application Firewall (WAF) rules to detect and block suspicious script injection attempts in administrative requests can provide an additional layer of defense. Regular security audits and scanning for XSS vulnerabilities in WordPress plugins should be integrated into the security lifecycle. For multisite environments, extra caution should be taken to review user privileges and ensure that only necessary users have high-level access. Finally, organizations should stay informed about updates from the plugin vendor and security advisories to apply patches promptly once available.