CVE-2025-27828 is a reflected cross-site scripting (XSS) vulnerability identified in the legacy chat component of Mitel MiContact Center Business versions up to 10.0.0.4, 10.1.0.0 through 10.1.0.5, and 10.2.0.0 through 10.2.0.4. This vulnerability arises due to insufficient input validation in the chat interface, allowing an unauthenticated attacker to inject malicious scripts that are reflected back to users. Exploitation requires user interaction, typically by tricking a user into clicking a crafted link or interacting with malicious content that triggers the reflected script execution. The impact of this vulnerability is limited, primarily affecting confidentiality and integrity to a minor degree, as the attacker can execute arbitrary scripts within the context of the victim's browser session. However, the vulnerability does not directly compromise system availability or allow for privilege escalation. Since the affected component is part of a contact center solution, exploitation could lead to session hijacking, phishing, or the theft of session cookies, potentially exposing sensitive communication data or user credentials. No known exploits are currently reported in the wild, and no official patches or CVSS scores have been published yet. The vulnerability is classified as reflected XSS, which is generally easier to exploit than stored XSS but requires social engineering to succeed.

For European organizations using Mitel MiContact Center Business, this vulnerability poses a moderate risk primarily to the confidentiality and integrity of user sessions within the contact center environment. Attackers could leverage this vulnerability to execute malicious scripts that steal session tokens, perform phishing attacks, or manipulate user interactions, potentially leading to unauthorized access to sensitive customer communications or internal data. Given the critical role of contact centers in customer service and operations, any compromise could damage organizational reputation and customer trust. However, the requirement for user interaction and the reflected nature of the XSS limits the scope of automated or widespread exploitation. The impact on availability is minimal, and the vulnerability does not directly enable system-level compromise. Organizations in sectors with high customer interaction volumes, such as telecommunications, finance, and public services, may face higher operational risks if exploited.

To mitigate this vulnerability effectively, European organizations should: 1) Implement strict input validation and output encoding on all user-supplied data in the chat component to prevent script injection. 2) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in the browser context. 3) Educate users and contact center agents about the risks of clicking on suspicious links or interacting with untrusted content. 4) Monitor web application logs for unusual input patterns or repeated attempts to exploit reflected XSS. 5) If possible, isolate the chat component within a sandboxed iframe to limit script execution scope. 6) Engage with Mitel for official patches or updates and prioritize their deployment once available. 7) Use web application firewalls (WAFs) with rules tailored to detect and block reflected XSS payloads targeting the chat interface. These measures go beyond generic advice by focusing on both technical controls and user awareness specific to the contact center environment.