CVE-2025-58787 is a security vulnerability classified as CWE-79, which corresponds to Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting (XSS). This vulnerability affects the Themify Popup plugin developed by themifyme, specifically versions up to and including 1.4.4. The vulnerability allows an attacker to inject malicious scripts that are stored and later executed in the context of a user's browser when they view the affected web page. This is a Stored XSS vulnerability, meaning the malicious payload is saved on the server side, for example in a database or persistent storage, and served to users without proper sanitization or encoding. The CVSS v3.1 base score for this vulnerability is 6.5, indicating a medium severity level. The vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) reveals that the attack can be performed remotely over the network (AV:N) with low attack complexity (AC:L), requires privileges (PR:L) and user interaction (UI:R), and impacts confidentiality, integrity, and availability to a limited extent (C:L/I:L/A:L). The scope is changed (S:C), meaning the vulnerability affects resources beyond the security scope of the vulnerable component. No known exploits in the wild have been reported yet, and no patches or fixes have been linked at the time of publication. The vulnerability arises because the plugin fails to properly neutralize or encode user-supplied input before rendering it in web pages, allowing malicious JavaScript or HTML to be executed in the browsers of users who view the affected content. This can lead to session hijacking, defacement, or redirection to malicious sites, among other impacts.

For European organizations using the Themify Popup plugin, this vulnerability poses a significant risk to web application security and user trust. Stored XSS can lead to the compromise of user sessions, theft of sensitive data such as authentication tokens or personal information, and unauthorized actions performed on behalf of users. This can result in data breaches, regulatory non-compliance (e.g., GDPR violations), reputational damage, and potential financial losses. Since the vulnerability requires some level of privilege to exploit (PR:L) and user interaction (UI:R), the risk is somewhat mitigated but still relevant, especially for organizations with many users or customers interacting with affected web pages. The changed scope (S:C) indicates that the impact could extend beyond the immediate plugin, potentially affecting other components or user accounts. European organizations in sectors such as e-commerce, finance, healthcare, and public services, which often rely on WordPress and associated plugins like Themify Popup for customer engagement, are particularly at risk. The lack of an available patch increases the urgency for mitigation to prevent exploitation. Additionally, the medium CVSS score suggests that while the vulnerability is not critical, it is sufficiently severe to warrant prompt attention.

1. Immediate mitigation should include disabling the Themify Popup plugin until a security patch is released by the vendor. 2. Implement Web Application Firewall (WAF) rules to detect and block typical XSS payloads targeting the affected plugin endpoints. 3. Conduct a thorough audit of all input fields and stored data handled by Themify Popup to identify and sanitize any malicious content already present. 4. Apply strict Content Security Policy (CSP) headers to restrict the execution of inline scripts and limit the domains from which scripts can be loaded, reducing the impact of potential XSS payloads. 5. Educate users and administrators about the risks of clicking suspicious links or interacting with untrusted content on affected sites. 6. Monitor web server and application logs for unusual activity or repeated attempts to exploit XSS vulnerabilities. 7. Once available, promptly apply official patches or updates from themifyme to remediate the vulnerability at the source. 8. Consider implementing additional input validation and output encoding mechanisms at the application level to prevent similar issues in the future.