CVE-2025-3302 is a high-severity Stored Cross-Site Scripting (XSS) vulnerability affecting the Xagio SEO – AI Powered SEO plugin for WordPress, specifically all versions up to and including 7.1.0.16. The vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. The root cause is insufficient sanitization and output escaping of the 'HTTP_REFERER' parameter, which is a common HTTP header that indicates the address of the webpage that linked to the resource being requested. Because the plugin fails to properly validate and encode this input, an unauthenticated attacker can inject arbitrary malicious scripts that become persistently stored within the plugin's output pages. These scripts execute in the browsers of any users who visit the affected pages, potentially leading to session hijacking, credential theft, defacement, or redirection to malicious sites. The vulnerability was partially addressed in version 7.1.0.0, but versions up to 7.1.0.16 remain vulnerable, indicating incomplete remediation. The CVSS v3.1 base score is 7.2, reflecting a high severity with network attack vector, low attack complexity, no privileges required, no user interaction needed, and a scope change, meaning the vulnerability affects resources beyond the initially vulnerable component. Confidentiality and integrity impacts are low but present, while availability is not affected. No known exploits are reported in the wild as of the publication date (June 11, 2025), but the ease of exploitation and unauthenticated access make this a significant risk for websites using this plugin. The vulnerability affects all installations of the plugin up to the specified versions, which are widely used in WordPress SEO management, making it a critical concern for website security.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of web applications relying on the Xagio SEO plugin. Exploitation could lead to unauthorized script execution in users' browsers, enabling theft of sensitive information such as authentication tokens, personal data, or corporate credentials. This can facilitate further attacks like account takeover or phishing campaigns targeting employees or customers. The persistent nature of stored XSS increases the attack surface and potential damage. Given the widespread use of WordPress in Europe, including by SMEs, public sector entities, and e-commerce platforms, the vulnerability could undermine trust, lead to data breaches, and cause regulatory compliance issues under GDPR due to unauthorized data exposure. Additionally, the scope change indicated in the CVSS vector suggests that the vulnerability could impact components beyond the plugin itself, potentially affecting other integrated services or plugins. The lack of required authentication and user interaction means attackers can exploit this remotely and at scale, increasing the threat level. Although no active exploits are currently known, the vulnerability's characteristics make it a likely target for attackers seeking to compromise European web assets.

European organizations should immediately assess their WordPress installations for the presence of the Xagio SEO – AI Powered SEO plugin and verify the version in use. The primary mitigation is to upgrade the plugin to a version beyond 7.1.0.16 where the vulnerability is fully patched. If an updated version is not yet available, organizations should consider temporarily disabling or uninstalling the plugin to eliminate exposure. Additionally, implement web application firewall (WAF) rules to detect and block malicious payloads targeting the 'HTTP_REFERER' parameter, focusing on script tags and suspicious input patterns. Conduct thorough input validation and output encoding on all user-controllable inputs at the application level as a defense-in-depth measure. Regularly scan websites for XSS vulnerabilities using automated tools and manual penetration testing. Educate web administrators and developers about secure coding practices related to input sanitization and output escaping. Monitor security advisories from the plugin vendor and WordPress community for updates or patches. Finally, review and enhance incident response plans to quickly address any exploitation attempts or breaches stemming from this vulnerability.