CVE-2025-67539 is a DOM-based Cross-site Scripting (XSS) vulnerability identified in the Select-Themes Select Core product, affecting all versions prior to 2.6. The root cause is improper neutralization of user-supplied input during web page generation, which allows attackers to inject malicious scripts that execute within the victim's browser context. Unlike traditional reflected or stored XSS, DOM-based XSS occurs entirely on the client side, exploiting the way JavaScript processes input data in the Document Object Model. This vulnerability can be triggered when a user visits a specially crafted URL or interacts with manipulated web page elements, leading to execution of arbitrary JavaScript code. Potential consequences include theft of session cookies, redirection to malicious sites, unauthorized actions performed with the victim's privileges, and potential compromise of user accounts. No authentication is required to exploit this vulnerability, but user interaction is necessary. Currently, no public exploits or patches have been released, but the vulnerability has been officially published and assigned a CVE identifier. The lack of a CVSS score indicates that further assessment is needed to understand the full scope and impact. However, given the nature of DOM-based XSS, it represents a significant risk to web applications relying on Select Core for dynamic content generation.

For European organizations, the impact of CVE-2025-67539 can be substantial, especially for those that deploy Select Core in customer-facing web applications or internal portals. Successful exploitation could lead to unauthorized access to sensitive user data, including personal information and authentication tokens, thereby violating GDPR requirements and potentially resulting in regulatory penalties. The integrity of user sessions and data could be compromised, leading to fraud, data leakage, or reputational damage. Availability is less directly affected but could be impacted if attackers use the vulnerability to perform further attacks such as phishing or malware distribution. Sectors such as finance, healthcare, e-commerce, and government services, which rely heavily on secure web interactions, are particularly vulnerable. The absence of known exploits currently provides a window for proactive mitigation, but the ease of exploitation via user interaction means that phishing campaigns or social engineering could rapidly leverage this vulnerability once publicized.

To mitigate CVE-2025-67539, European organizations should prioritize the following actions: 1) Monitor Select-Themes official channels for patches and apply updates to Select Core promptly once available, ensuring version 2.6 or later is deployed. 2) Implement strict input validation and output encoding on all user-supplied data processed by web applications to prevent injection of malicious scripts. 3) Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS attacks. 4) Conduct regular security testing, including automated scanning and manual code reviews, focusing on client-side JavaScript handling and DOM manipulation. 5) Educate users about the risks of clicking on suspicious links and implement email filtering to reduce phishing attempts that could exploit this vulnerability. 6) Use web application firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting Select Core. 7) Review and harden session management practices to limit the damage from stolen session tokens. These measures combined will reduce the likelihood and impact of exploitation.