CVE-2025-58018 is a Stored Cross-Site Scripting (XSS) vulnerability classified under CWE-79, affecting the Richard Leishman Mail Subscribe List software up to version 2.1.10. This vulnerability arises from improper neutralization of user input during web page generation, allowing an attacker to inject malicious scripts that are stored and later executed in the context of users visiting the affected web pages. The vulnerability is exploitable remotely over the network (AV:N) with low attack complexity (AC:L), but requires some level of privileges (PR:L) and user interaction (UI:R) to trigger. 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 (C:L/I:L/A:L), reflecting that the attacker can potentially steal user session data, manipulate displayed content, or cause partial service disruption. No known public exploits are reported yet, and no patches are currently linked, indicating that mitigation may require manual intervention or vendor updates. Stored XSS vulnerabilities are particularly dangerous because malicious scripts persist on the server and affect multiple users, potentially leading to credential theft, session hijacking, or distribution of malware. The affected product, Mail Subscribe List, is a mailing list management tool used to collect and manage email subscriptions, often embedded in websites to facilitate newsletter signups. The vulnerability likely stems from insufficient input validation or output encoding when processing subscription data or displaying subscriber information on web pages.

For European organizations using the Richard Leishman Mail Subscribe List, this vulnerability poses a moderate risk. Exploitation could lead to compromise of user accounts, leakage of sensitive subscriber information, and erosion of trust in the organization's communication channels. Attackers could leverage the stored XSS to execute phishing attacks, spread malware, or perform session hijacking against subscribers or administrators. This could result in reputational damage, regulatory scrutiny under GDPR due to potential personal data exposure, and operational disruptions if the mailing list service is critical for customer engagement. Organizations in sectors with high reliance on email marketing or subscriber communications, such as e-commerce, media, and public services, may face amplified risks. The requirement for some privileges and user interaction reduces the likelihood of widespread automated exploitation but does not eliminate targeted attacks, especially against high-value targets.

European organizations should prioritize the following mitigations: 1) Immediately audit and sanitize all user inputs related to subscription forms and subscriber data display, implementing strict input validation and context-aware output encoding to prevent script injection. 2) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 3) Monitor and review mailing list content regularly for suspicious or unexpected scripts or HTML. 4) Limit privileges required to manage subscription data to trusted personnel and enforce strong authentication mechanisms. 5) If possible, upgrade to a patched version once available or apply vendor-recommended fixes promptly. 6) Educate users and administrators about the risks of XSS and encourage cautious interaction with unexpected content. 7) Implement web application firewalls (WAF) with rules designed to detect and block XSS payloads targeting the Mail Subscribe List application. These steps go beyond generic advice by focusing on the specific context of mailing list management and stored XSS risks.