CVE-2025-57903 is a medium severity vulnerability classified under CWE-79, which pertains to Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting (XSS). This vulnerability affects the WordPress plugin 'WooCommerce Additional Fees On Checkout (Free)' developed by WPSuperiors Developer, specifically versions up to 1.5.0. The flaw allows an attacker to inject malicious scripts that are stored and later executed in the context of users visiting affected web pages. The vulnerability is a Stored XSS, meaning the malicious payload is saved on the server and delivered to users without proper sanitization or encoding. The CVSS 3.1 base score is 5.9, indicating a medium severity level, with the vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L. This vector indicates that the attack can be performed remotely over the network, requires low attack complexity, but does require high privileges and user interaction. The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The impact includes low confidentiality, integrity, and availability impacts, as the attacker can execute scripts that may steal user data, manipulate content, or perform actions on behalf of the user. However, exploitation requires authenticated access and user interaction, limiting the attack surface. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability arises due to insufficient input validation and output encoding during web page generation in the plugin, allowing malicious JavaScript to be stored and executed in users' browsers.

For European organizations using WooCommerce with the vulnerable 'Additional Fees On Checkout (Free)' plugin, this vulnerability poses a risk of session hijacking, theft of sensitive customer data, and unauthorized actions performed under the context of authenticated users. Since WooCommerce is widely used for e-commerce in Europe, especially by small and medium-sized enterprises, exploitation could lead to reputational damage, financial loss, and regulatory penalties under GDPR if personal data is compromised. The requirement for attacker authentication and user interaction reduces the likelihood of mass exploitation but targeted attacks against administrators or privileged users could facilitate further compromise of the e-commerce platform. Additionally, the scope change in the vulnerability suggests that the impact could extend beyond the plugin itself, potentially affecting other parts of the website or connected systems. European organizations with high transaction volumes or those handling sensitive payment information should be particularly cautious, as any compromise could disrupt business operations and customer trust.

To mitigate this vulnerability, European organizations should: 1) Immediately audit their WooCommerce installations to identify if the vulnerable 'Additional Fees On Checkout (Free)' plugin version 1.5.0 or earlier is in use. 2) Disable or remove the plugin until an official patch or update is released by WPSuperiors Developer. 3) Implement strict input validation and output encoding on all user-supplied data within the plugin or custom code to prevent script injection. 4) Enforce the principle of least privilege by limiting administrative access to trusted personnel only, reducing the risk of an attacker gaining the required high privileges. 5) Monitor web server and application logs for suspicious activity indicative of XSS exploitation attempts, such as unusual POST requests or script injections. 6) Educate administrators and users about the risks of interacting with unexpected or suspicious content within the admin interface. 7) Consider deploying a Web Application Firewall (WAF) with rules to detect and block XSS payloads targeting the affected plugin endpoints. 8) Once available, promptly apply vendor patches or updates addressing this vulnerability. 9) Conduct regular security assessments and penetration testing focusing on web application input handling and session management.