CVE-2025-3867 is a security vulnerability identified in the Ajax Comment Form CST plugin for WordPress, developed by rafe007. This vulnerability is classified under CWE-79, which corresponds to improper neutralization of input during web page generation, commonly known as Cross-Site Scripting (XSS). The root cause of this vulnerability is a Cross-Site Request Forgery (CSRF) flaw due to missing or incorrect nonce validation on the 'acform_cst_settings' administrative page. Nonce validation is a security mechanism used to ensure that requests made to a web application are intentional and authorized. In this case, the absence or incorrect implementation of nonce validation allows an unauthenticated attacker to craft a malicious request that can update plugin settings. This update can inject malicious scripts into the web application, which will be executed in the context of the administrator's browser session if the administrator is tricked into clicking a specially crafted link or visiting a malicious web page. The vulnerability affects all versions of the Ajax Comment Form CST plugin up to and including version 1.2, with no patch currently available. Although no known exploits are reported in the wild, the vulnerability poses a significant risk because it allows unauthorized modification of plugin settings and potential execution of arbitrary scripts with administrative privileges. Exploitation requires social engineering to convince an administrator to perform an action, but no authentication is required to initiate the attack. This vulnerability can lead to session hijacking, privilege escalation, defacement, or further compromise of the WordPress site and its users.

For European organizations using WordPress sites with the Ajax Comment Form CST plugin, this vulnerability could lead to unauthorized administrative control over plugin settings, enabling attackers to inject malicious scripts that compromise site integrity and user data confidentiality. The impact includes potential theft of administrator credentials, session hijacking, and the spread of malware or phishing attacks through compromised sites. This can damage organizational reputation, lead to regulatory non-compliance (e.g., GDPR violations due to data breaches), and disrupt business operations. Given the widespread use of WordPress across Europe, especially among SMEs and public sector entities, the vulnerability could be leveraged to target high-value sites with sensitive data or critical services. The requirement for social engineering reduces the attack surface but does not eliminate risk, as phishing remains a common and effective attack vector. The absence of a patch increases exposure time, making timely mitigation essential.

Immediately audit all WordPress sites for the presence of the Ajax Comment Form CST plugin and identify versions in use. Disable or remove the Ajax Comment Form CST plugin until a secure patched version is released. Implement strict administrative access controls and limit plugin management privileges to trusted personnel only. Educate administrators and site managers about the risk of social engineering attacks, emphasizing caution when clicking on unsolicited links or opening suspicious emails. Use web application firewalls (WAFs) with custom rules to detect and block suspicious requests targeting the 'acform_cst_settings' endpoint. Monitor web server and application logs for unusual POST requests or changes to plugin settings that could indicate exploitation attempts. Apply Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts on WordPress sites. Regularly update WordPress core, plugins, and themes to minimize exposure to known vulnerabilities. Prepare incident response plans specific to web application compromises to enable rapid containment and remediation.