CVE-2025-48483 is a medium-severity vulnerability affecting FreeScout, a free and self-hosted help desk and shared mailbox application. The vulnerability is classified as a Cross-Site Scripting (XSS) flaw (CWE-79) caused by improper neutralization of user input during mail signature sanitization prior to version 1.8.180. Specifically, FreeScout versions before 1.8.180 do not correctly validate or sanitize user-supplied data embedded in mail signatures, allowing an attacker to inject arbitrary HTML or JavaScript code. When a user views an email containing a maliciously crafted signature, the injected script executes in the context of the victim's browser. This can lead to theft of sensitive information such as session cookies, unauthorized actions on behalf of the user, or other malicious activities. Furthermore, if an administrator opens an email with a malicious signature, the XSS vulnerability can be chained with a Cross-Site Request Forgery (CSRF) attack (CWE-352), potentially enabling attackers to perform unauthorized administrative actions. The vulnerability requires no authentication but does require user interaction (viewing the malicious email). The CVSS 4.0 base score is 6.3, reflecting a medium severity with network attack vector, low attack complexity, no privileges required, but user interaction needed. The vulnerability has been patched in FreeScout version 1.8.180. No known exploits are currently reported in the wild. This vulnerability highlights the risks of insufficient input sanitization in web applications that process user-generated content, especially in email and help desk platforms where trust boundaries are critical.

For European organizations using FreeScout as a help desk or shared mailbox solution, this vulnerability poses a significant risk to confidentiality and integrity of sensitive communications. An attacker exploiting this flaw could steal session tokens or other sensitive data from users, potentially leading to account compromise. The chaining with CSRF attacks could allow attackers to escalate privileges or perform unauthorized administrative actions, disrupting help desk operations or exposing sensitive customer data. Given that FreeScout is self-hosted, organizations with less mature patch management or security monitoring may be particularly vulnerable. The impact is heightened in sectors handling sensitive personal data under GDPR, such as healthcare, finance, or public administration, where data breaches can result in regulatory penalties and reputational damage. Additionally, the reliance on email workflows in customer support means that exploitation could disrupt business continuity and trust. Although no active exploits are known, the medium severity and ease of exploitation via crafted emails necessitate prompt remediation to prevent targeted attacks or phishing campaigns leveraging this vulnerability.

European organizations should immediately verify their FreeScout version and upgrade to version 1.8.180 or later, where the vulnerability is patched. Until upgrade is possible, organizations should implement strict email filtering and sanitization policies to detect and block emails containing suspicious or malformed signatures. Employing Content Security Policy (CSP) headers can help mitigate the impact of XSS by restricting script execution contexts. Administrators should be trained to recognize phishing attempts and avoid opening suspicious emails, especially those with unusual signatures. Regular security audits and penetration testing of the help desk environment can identify residual risks. Additionally, organizations should monitor logs for unusual administrative actions that could indicate exploitation attempts. Network segmentation of the help desk system and limiting administrative access to trusted networks can reduce attack surface. Finally, implementing multi-factor authentication (MFA) for administrative accounts can mitigate the risk of session hijacking resulting from XSS attacks.