CVE-2025-62752 identifies a DOM-based Cross-site Scripting (XSS) vulnerability in the kalender.digital Calendar.online / Kalender.digital product line, affecting versions up to 1.0.11. This vulnerability is categorized under CWE-79, which involves improper neutralization of input during web page generation. Specifically, the issue arises when user-supplied input is not correctly sanitized or encoded before being incorporated into the Document Object Model (DOM), allowing attackers to inject malicious JavaScript code. When a victim interacts with a crafted link or input, the malicious script executes in their browser context, potentially leading to session hijacking, credential theft, or unauthorized actions within the calendar application. The vulnerability requires low attack complexity and privileges (PR:L), but does require user interaction (UI:R). The CVSS 3.1 vector indicates network attack vector (AV:N), low attack complexity (AC:L), privileges required (PR:L), user interaction required (UI:R), and a scope change (S:C), with partial impacts on confidentiality, integrity, and availability (C:L/I:L/A:L). No public exploits or patches are currently available, but the vulnerability is published and recognized by Patchstack. The affected product is a web-based calendar service, which is commonly used for scheduling and collaboration, making it a valuable target for attackers aiming to disrupt operations or steal sensitive information.

For European organizations, the impact of this DOM-based XSS vulnerability can be significant, especially for those relying on kalender.digital's Calendar.online / Kalender.digital services for internal and external scheduling. Successful exploitation could lead to unauthorized access to user sessions, enabling attackers to impersonate users, access sensitive calendar data, or inject malicious content that spreads further within the organization. This could result in data confidentiality breaches, manipulation of calendar events, or disruption of business operations. Given the collaborative nature of calendar applications, attackers might leverage this vulnerability to conduct phishing attacks or deliver malware payloads. The medium CVSS score reflects a moderate risk, but the scope change and potential for chained attacks elevate the concern. European entities in sectors such as government, finance, and critical infrastructure, which often use web-based collaboration tools, could face operational and reputational damage if exploited.

To mitigate CVE-2025-62752, European organizations should: 1) Monitor kalender.digital vendor communications closely and apply security patches promptly once released. 2) Implement strict input validation and output encoding on all user-supplied data within the calendar application to prevent script injection. 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 assessments and penetration testing focused on web application vulnerabilities, including DOM-based XSS. 5) Educate users about the risks of clicking on suspicious links or inputs that could trigger XSS payloads. 6) Consider isolating calendar services in segmented network zones to limit lateral movement if exploitation occurs. 7) Utilize web application firewalls (WAFs) with updated signatures to detect and block XSS attack patterns targeting the affected product. These measures, combined with vigilant monitoring, will reduce the likelihood and impact of exploitation.