CVE-2025-3890 is a Stored Cross-Site Scripting (XSS) vulnerability affecting the WordPress Simple Shopping Cart plugin developed by mra13. This vulnerability exists in all versions up to and including 5.1.3. The root cause is improper neutralization of input during web page generation, specifically insufficient sanitization and output escaping of user-supplied attributes within the plugin's 'wp_cart_button' shortcode. An authenticated attacker with contributor-level privileges or higher can exploit this flaw by injecting malicious JavaScript code into pages where the shortcode is used. Because the injected script is stored persistently, it executes whenever any user accesses the compromised page, potentially leading to session hijacking, privilege escalation, or other malicious actions. The vulnerability has a CVSS 3.1 base score of 6.4, indicating a medium severity level. The attack vector is network-based with low attack complexity, requiring privileges equivalent to contributor access, and no user interaction is needed for the exploit to succeed. The scope is changed, meaning the vulnerability affects resources beyond the initially vulnerable component. No known exploits are currently reported in the wild, and no official patches have been linked yet. This vulnerability falls under CWE-79, which covers improper neutralization of input leading to XSS attacks. Given the widespread use of WordPress and the popularity of e-commerce plugins, this vulnerability poses a significant risk to websites using the affected plugin versions, especially those that allow multiple contributors to publish content.

For European organizations, the impact of this vulnerability can be substantial, particularly for businesses relying on WordPress-based e-commerce platforms using the Simple Shopping Cart plugin. Exploitation can lead to the injection of malicious scripts that compromise user sessions, steal sensitive customer data, or manipulate website content, undermining customer trust and potentially violating data protection regulations such as GDPR. The integrity of web content can be compromised, leading to reputational damage and financial losses. Since the vulnerability requires contributor-level access, insider threats or compromised contributor accounts increase risk. The vulnerability does not directly affect availability but can indirectly cause service disruptions if exploited for further attacks or if remediation requires downtime. Organizations in sectors with high online transaction volumes, such as retail, hospitality, and digital services, are particularly vulnerable. Additionally, the cross-site scripting can be leveraged to deliver further attacks like phishing or malware distribution, amplifying the threat landscape for European entities.

1. Immediate mitigation involves restricting contributor-level access to trusted users only and reviewing existing contributor accounts for suspicious activity. 2. Implement strict input validation and output encoding on all user-generated content, especially for shortcode attributes, either through plugin updates or custom code patches. 3. Monitor web application logs for unusual script injections or anomalous behavior indicative of exploitation attempts. 4. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts on affected pages. 5. Use Web Application Firewalls (WAFs) configured to detect and block XSS payloads targeting the 'wp_cart_button' shortcode. 6. Regularly update WordPress core and plugins; although no patch is currently linked, monitor the vendor’s channels for forthcoming fixes and apply them promptly. 7. Conduct security awareness training for contributors to reduce the risk of credential compromise and social engineering. 8. Consider isolating or disabling the vulnerable shortcode if immediate patching is not feasible, to prevent exploitation.