CVE-2023-4687 is a Cross-Site Scripting (XSS) vulnerability identified in the WordPress plugin "Page Builder: Pagelayer," specifically affecting versions prior to 1.7.7, including version 1.3.2. The vulnerability arises because the plugin fails to properly restrict unauthenticated attackers from updating the header or footer code of scheduled posts. This improper validation allows attackers to inject malicious scripts into these sections, which are then executed in the context of users visiting the affected WordPress site. The vulnerability is classified under CWE-79, indicating a classic reflected or stored XSS issue. The CVSS v3.1 base score is 6.1 (medium severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The impact affects confidentiality and integrity at a low level, with no impact on availability. No known exploits are currently reported in the wild, and no official patches are linked, though the vulnerability is addressed in versions after 1.7.7. The vulnerability's exploitation could allow attackers to execute arbitrary JavaScript in the browsers of users who view the compromised scheduled posts, potentially leading to session hijacking, defacement, or redirection to malicious sites. Since the attack vector is unauthenticated and network-based, it poses a significant risk to websites using the vulnerable plugin versions, especially those with scheduled posts that include header or footer code modifications.

For European organizations, especially those relying on WordPress websites with the Page Builder: Pagelayer plugin, this vulnerability poses a risk of client-side attacks that can compromise user trust and data confidentiality. The injection of malicious scripts could lead to theft of session cookies, user credentials, or the spread of malware to visitors, including customers or employees accessing the site. This can damage the organization's reputation, lead to regulatory non-compliance under GDPR if personal data is compromised, and potentially cause financial losses. Since the vulnerability allows unauthenticated attackers to modify scheduled posts, attackers could automate the injection of malicious payloads that activate at specific times, increasing the attack's stealth and impact. The medium severity score reflects moderate risk, but the ease of exploitation without authentication and the potential for widespread impact on site visitors elevate the concern. Organizations in sectors such as e-commerce, media, government, and education, which often use WordPress extensively, may be particularly affected. Additionally, the vulnerability could be leveraged as part of a broader attack chain targeting European users or organizations.

1. Immediate upgrade of the Page Builder: Pagelayer plugin to version 1.7.7 or later, where the vulnerability is fixed, is the primary mitigation step. 2. If upgrading is not immediately possible, restrict access to the WordPress admin and scheduled post editing interfaces using IP whitelisting or VPN access to prevent unauthorized changes. 3. Implement Web Application Firewall (WAF) rules to detect and block suspicious payloads targeting header or footer code injection points. 4. Conduct a thorough audit of scheduled posts to identify and remove any unauthorized or suspicious header/footer code injections. 5. Enable Content Security Policy (CSP) headers on the website to limit the execution of unauthorized scripts, mitigating the impact of potential XSS payloads. 6. Monitor website traffic and logs for unusual activity or spikes in scheduled post modifications. 7. Educate site administrators about the risks of using outdated plugins and the importance of timely updates. 8. Consider disabling or limiting the use of scheduled posts with custom header/footer code if not essential. 9. Regularly back up website content and configurations to enable quick restoration in case of compromise.