CVE-2025-3866 is a vulnerability affecting the WordPress plugin 'Add Google +1 (Plus one) social share Button' developed by rohanpawale. The vulnerability is classified under CWE-79, which corresponds to improper neutralization of input during web page generation, commonly known as Cross-Site Scripting (XSS). Specifically, this vulnerability arises due to missing or incorrect nonce validation on the 'google-plus-one-share-button' page. Nonces are security tokens used in WordPress to verify that requests are intentional and originate from legitimate users. The absence or improper implementation of nonce validation allows an attacker to perform Cross-Site Request Forgery (CSRF) attacks. Through CSRF, an unauthenticated attacker can craft a malicious request that, if executed by a site administrator (for example, by clicking a link), can update plugin settings and inject malicious scripts into the website. This injection can lead to the execution of arbitrary JavaScript in the context of the administrator's browser session, potentially compromising site integrity and user data. The vulnerability affects all versions up to and including 1.0.0 of the plugin. No patches or fixes have been published yet, and there are no known exploits in the wild at the time of reporting. The attack requires tricking an authenticated administrator into performing an action, which implies user interaction is necessary. The vulnerability impacts the confidentiality, integrity, and availability of the affected WordPress sites by enabling script injection and unauthorized configuration changes.

For European organizations using WordPress websites with the 'Add Google +1 (Plus one) social share Button' plugin, this vulnerability presents a moderate risk. Successful exploitation can lead to unauthorized changes in plugin settings and injection of malicious scripts, which may result in defacement, theft of administrator credentials via session hijacking, or distribution of malware to site visitors. This can damage organizational reputation, lead to data breaches, and disrupt web services. Since the attack requires an administrator to be tricked into clicking a malicious link, social engineering is a critical factor. Organizations with public-facing WordPress sites, especially those in sectors like e-commerce, government, media, and education, may face increased risks due to the potential for targeted phishing campaigns. The impact on confidentiality is significant if session tokens or sensitive data are exposed. Integrity is compromised through unauthorized script injection and configuration changes. Availability impact is moderate, as injected scripts could disrupt site functionality or cause downtime. However, the lack of known active exploits reduces immediate risk, though the presence of the vulnerability in all plugin versions means many sites could be exposed if attackers develop exploits.

1. Immediate removal or deactivation of the 'Add Google +1 (Plus one) social share Button' plugin until a secure version is released. 2. Monitor official plugin repositories and vendor communications for patches or updates addressing this vulnerability. 3. Implement strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts on WordPress sites. 4. Educate site administrators on phishing and social engineering risks to reduce the likelihood of clicking malicious links. 5. Employ multi-factor authentication (MFA) for WordPress administrator accounts to mitigate the risk of credential compromise. 6. Regularly audit WordPress plugins and themes for vulnerabilities and remove unused or unsupported plugins. 7. Use security plugins that can detect and block suspicious requests or changes to plugin settings. 8. Conduct periodic security assessments and penetration testing focusing on web application vulnerabilities including CSRF and XSS. 9. Restrict administrative access by IP whitelisting or VPN to reduce exposure to external attacks. 10. Backup website data and configurations regularly to enable quick recovery in case of compromise.