CVE-2025-9816 is a stored cross-site scripting (XSS) vulnerability identified in the WP Statistics plugin for WordPress, a privacy-focused alternative to Google Analytics developed by veronalabs. The vulnerability exists in all plugin versions up to and including 14.5.4. It stems from insufficient input sanitization and output escaping of the User-Agent HTTP header, which is logged and displayed by the plugin without proper neutralization. An unauthenticated attacker can craft a malicious User-Agent string containing arbitrary JavaScript code. When this malicious header is stored and later rendered on administrative or user-facing pages, the embedded script executes in the context of the victim’s browser. This can lead to session hijacking, theft of sensitive data, or execution of further malicious actions within the victim’s session. The vulnerability is exploitable remotely over the network without any authentication or user interaction, increasing its severity. The CVSS v3.1 base score is 7.2, reflecting high impact on confidentiality and integrity with no impact on availability. The scope is considered changed (S:C) because the vulnerability affects components beyond the vulnerable plugin itself, potentially impacting the entire WordPress site. No patches or official fixes are currently linked, and no active exploitation has been reported, but the risk remains high due to the plugin’s popularity and the ease of exploitation.

The impact of CVE-2025-9816 is significant for organizations using the WP Statistics plugin. Successful exploitation allows attackers to execute arbitrary scripts in the context of users visiting affected pages, potentially leading to credential theft, session hijacking, defacement, or distribution of malware. This compromises the confidentiality and integrity of user data and site content. Since the vulnerability requires no authentication and can be triggered remotely, it poses a high risk to websites, especially those with multiple users or administrators accessing the statistics pages. The widespread adoption of WordPress and this plugin increases the potential attack surface globally. Organizations may suffer reputational damage, data breaches, and regulatory consequences if user data is exposed. Additionally, attackers could leverage this vulnerability as a foothold for further attacks within the network or to pivot to other systems.

To mitigate CVE-2025-9816, organizations should immediately update the WP Statistics plugin to a patched version once available. In the absence of an official patch, administrators should implement strict input validation and output encoding on all user-controllable inputs, especially the User-Agent header before logging or rendering. Web application firewalls (WAFs) can be configured to detect and block suspicious User-Agent strings containing script tags or other malicious payloads. Restricting access to statistics pages to trusted users only and employing Content Security Policy (CSP) headers can reduce the risk of script execution. Regular monitoring of logs for unusual User-Agent entries and scanning for injected scripts on pages is advised. Additionally, educating site administrators about the risks of XSS and ensuring WordPress core and all plugins are kept up to date will help reduce exposure to similar vulnerabilities.