CVE-2022-3906 is a Stored Cross-Site Scripting (XSS) vulnerability identified in the Easy Form Builder WordPress plugin versions prior to 3.4.0. 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 unfiltered_html capability is disabled, such as in multisite environments, which typically restricts the ability to post unfiltered HTML. The attack vector requires the attacker to have authenticated access with high privileges, and user interaction is necessary to trigger the malicious script execution. The vulnerability impacts confidentiality and integrity by enabling potential theft of session cookies, credentials, or manipulation of site content through script execution in the context of the victim's browser. However, it does not affect availability. The CVSS 3.1 base score is 4.8 (medium severity), reflecting network attack vector, low attack complexity, high privileges required, user interaction required, and partial impact on confidentiality and integrity. There are no known exploits in the wild, and no official patches or vendor information is currently available. The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation), a common web security weakness related to XSS attacks.

For European organizations using WordPress sites with the Easy Form Builder plugin, this vulnerability poses a moderate risk. Attackers with administrative access could inject malicious scripts that execute in the browsers of other users, potentially leading to session hijacking, unauthorized actions, or data leakage. This is particularly concerning for organizations with multisite WordPress deployments, such as universities, media companies, or government portals, where multiple users access shared administrative interfaces. The impact on confidentiality and integrity could lead to reputational damage, compliance violations (e.g., GDPR), and unauthorized access to sensitive information. However, since exploitation requires high privileges and user interaction, the risk is somewhat mitigated by internal access controls and user awareness. The absence of known exploits reduces immediate threat but does not eliminate the risk, especially if attackers gain administrative credentials via other means. The vulnerability does not affect system availability, so denial-of-service impacts are unlikely.

1. Immediate mitigation should include upgrading the Easy Form Builder plugin to version 3.4.0 or later once available, as this version addresses the sanitization and escaping issues. 2. Until an official patch is released, restrict administrative access to trusted personnel only and enforce strong authentication mechanisms such as multi-factor authentication (MFA) to reduce the risk of credential compromise. 3. Conduct a thorough audit of all stored settings in the plugin to identify and remove any suspicious or unauthorized scripts. 4. Implement Content Security Policy (CSP) headers to limit the execution of unauthorized scripts within the WordPress environment. 5. Monitor logs for unusual administrative activities or attempts to inject scripts. 6. Educate administrators about the risks of XSS and the importance of validating inputs even with high privileges. 7. Consider isolating multisite environments or limiting plugin usage to reduce the attack surface. 8. Regularly back up WordPress sites to enable recovery in case of compromise.