CVE-2021-38347 is a reflected Cross-Site Scripting (XSS) vulnerability affecting the Custom Website Data WordPress plugin, specifically versions up to and including 2.2. The vulnerability exists in the ~/views/edit.php file where the 'id' parameter is not properly sanitized or validated, allowing an attacker to inject arbitrary malicious scripts. When a victim user accesses a crafted URL containing the malicious payload in the 'id' parameter, the injected script executes in the context of the victim's browser. This can lead to theft of session cookies, defacement, or redirection to malicious sites. 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 an attack vector of network (remote), low attack complexity, no privileges required, but user interaction is necessary (the victim must click a malicious link). The scope is changed, meaning the vulnerability can affect resources beyond the vulnerable component, potentially impacting the confidentiality and integrity of user data. There are no known public exploits in the wild, and no official patches or updates have been linked in the provided data. The plugin is used within WordPress environments, which are widely deployed across many European organizations for website content management and customer engagement.

For European organizations, this vulnerability poses a moderate risk primarily to the confidentiality and integrity of web session data and user interactions on affected websites. Exploitation could allow attackers to hijack user sessions, steal sensitive information, or perform actions on behalf of authenticated users, potentially leading to unauthorized access or data leakage. This is particularly concerning for organizations handling personal data under GDPR regulations, as exploitation could result in data breaches with legal and reputational consequences. Additionally, compromised websites could be used to distribute malware or conduct phishing campaigns targeting European users. The reflected nature of the XSS means attacks require user interaction, typically via social engineering, but the widespread use of WordPress and the plugin increases the attack surface. The vulnerability does not directly impact availability but can undermine trust in affected web services and lead to indirect operational disruptions.

1. Immediate mitigation involves disabling or removing the Custom Website Data plugin version 2.2 or earlier until a patched version is available. 2. Implement Web Application Firewall (WAF) rules specifically targeting suspicious input patterns in the 'id' parameter to block malicious payloads. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts on affected websites, mitigating the impact of XSS attacks. 4. Conduct thorough input validation and sanitization on all user-supplied parameters, especially 'id', to prevent script injection. 5. Educate website administrators and users about the risks of clicking on untrusted links to reduce the likelihood of successful social engineering exploitation. 6. Monitor web server logs for unusual requests containing suspicious script patterns in URL parameters. 7. Keep WordPress core, themes, and plugins updated regularly and subscribe to vendor security advisories for timely patching. 8. Consider deploying security plugins that provide XSS protection and scanning capabilities to detect vulnerable components.