CVE-2025-58821 is a medium-severity Stored Cross-Site Scripting (XSS) vulnerability affecting the WordPress plugin WP Notification Bell developed by wpdever. The vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. Specifically, the plugin fails to adequately sanitize or encode user-supplied input before rendering it in the web interface, allowing an attacker with appropriate privileges to inject malicious scripts that persist in the application. The vulnerability affects versions up to and including 1.4.5, with no specific earliest affected version identified. Exploitation requires an attacker to have high privileges (PR:H) and user interaction (UI:R), such as tricking a user to click a crafted link or visit a malicious page. The vulnerability has a CVSS v3.1 base score of 5.9, indicating a medium severity level. The vector indicates network attack vector (AV:N), low attack complexity (AC:L), and scope change (S:C), meaning the impact extends beyond the vulnerable component. The impact affects confidentiality, integrity, and availability at a low level. No known exploits are currently reported in the wild, and no patches have been linked yet. Stored XSS can lead to session hijacking, defacement, or redirection to malicious sites, especially dangerous in WordPress environments where administrative users manage website content and plugins. Since exploitation requires high privileges, the threat is more relevant in scenarios where an attacker has already compromised or gained elevated access to the WordPress backend or user accounts with sufficient rights to inject content. This vulnerability highlights the importance of input validation and output encoding in WordPress plugin development to prevent persistent script injection attacks.

For European organizations using WordPress websites with the WP Notification Bell plugin, this vulnerability poses a moderate risk. Stored XSS can enable attackers to execute arbitrary JavaScript in the context of the affected site, potentially leading to session hijacking of administrators or users, unauthorized actions, or distribution of malware. Given that exploitation requires high privileges, the primary risk is from insider threats or attackers who have already breached lower-level accounts. The compromise of administrative sessions could lead to website defacement, data leakage, or further malware implantation, affecting brand reputation and user trust. In sectors such as finance, healthcare, or government within Europe, where data protection regulations like GDPR impose strict requirements, such breaches could result in regulatory penalties and loss of customer confidence. Additionally, the scope change in the CVSS vector suggests that the vulnerability could impact components beyond the plugin itself, potentially affecting the entire WordPress site’s security posture. Although no active exploits are reported, the medium severity and ease of network access mean European organizations should proactively address this vulnerability to prevent escalation of privileges or lateral movement within their web infrastructure.

European organizations should immediately audit their WordPress installations to identify the presence of the WP Notification Bell plugin, especially versions up to 1.4.5. Until an official patch is released, administrators should consider disabling or uninstalling the plugin to eliminate the attack surface. Implement strict role-based access controls to limit the number of users with high privileges capable of injecting content. Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious input patterns associated with XSS attacks targeting this plugin. Regularly monitor logs for unusual activity or injection attempts related to notification content. Educate administrators and users about phishing and social engineering tactics that could facilitate user interaction required for exploitation. Once a patch becomes available, prioritize its deployment in all affected environments. Additionally, implement Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS payloads. Conduct periodic security assessments and code reviews of WordPress plugins to identify similar input validation issues proactively.