CVE-2025-13515 identifies a reflected Cross-Site Scripting (XSS) vulnerability in the Nouri.sh Newsletter plugin for WordPress, versions up to and including 1.0.1.3. The vulnerability stems from insufficient sanitization and escaping of the $_SERVER['PHP_SELF'] parameter during web page generation. This parameter is commonly used to reference the current script's filename, but if not properly neutralized, it can be manipulated by attackers to inject arbitrary JavaScript code. Because the vulnerability is reflected, the malicious payload is embedded in a crafted URL that, when clicked by a user, causes the injected script to execute in the context of the vulnerable website. The attack does not require authentication but does require user interaction (clicking a link). The CVSS 3.1 base score of 6.1 reflects a medium severity, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), scope changed (S:C), and impacts on confidentiality and integrity (C:L/I:L) but not availability (A:N). The scope change indicates the vulnerability affects resources beyond the vulnerable component, potentially impacting the broader site or user session. No public exploits are currently known, and no patches have been linked yet, suggesting the need for vigilance and proactive mitigation. The vulnerability falls under CWE-79, a common and well-understood class of injection flaws that can lead to session hijacking, defacement, or redirection to malicious sites.

For European organizations, the impact of this vulnerability primarily concerns the confidentiality and integrity of user data and sessions. Attackers can exploit the reflected XSS to steal cookies, session tokens, or other sensitive information from users interacting with affected newsletter pages. This can lead to account compromise, unauthorized actions, or phishing attacks leveraging the trusted site context. Although availability is not directly impacted, successful exploitation can damage organizational reputation and user trust, especially for companies relying on newsletters for customer engagement. Public-facing WordPress sites using the Nouri.sh Newsletter plugin are at risk, particularly those with large subscriber bases or handling sensitive user information. The medium severity score suggests a moderate risk, but the ease of exploitation and lack of required privileges increase the threat level. European data protection regulations such as GDPR also impose obligations to protect user data, making exploitation potentially costly in terms of compliance and fines.

1. Monitor for official patches or updates from the Nouri.sh Newsletter plugin vendor and apply them promptly once released. 2. Until patches are available, implement Web Application Firewall (WAF) rules to detect and block suspicious requests containing malicious payloads targeting the $_SERVER['PHP_SELF'] parameter. 3. Employ strict input validation and output encoding on all user-controllable inputs, especially URL parameters, to neutralize script injection attempts. 4. Configure Content Security Policy (CSP) headers to restrict the execution of inline scripts and loading of untrusted resources, mitigating the impact of XSS attacks. 5. Educate users and administrators about the risks of clicking unsolicited or suspicious links, particularly those related to newsletters or email campaigns. 6. Regularly audit WordPress plugins for vulnerabilities and consider alternative plugins with better security track records if timely patches are not forthcoming. 7. Use security plugins that can detect and block XSS attempts and monitor logs for unusual activity related to the newsletter pages.