CVE-2025-4599 is a Cross-Site Scripting (XSS) vulnerability identified in the fragment preview functionality of Liferay Portal versions 7.4.3.61 through 7.4.3.132 and multiple versions of Liferay DXP 2024 quarterly releases. The vulnerability arises due to improper neutralization of input during web page generation, specifically involving the postMessage API. This flaw allows a remote attacker, without requiring authentication, to inject malicious JavaScript code into the fragment portlet URL. When a victim accesses the affected fragment preview, the injected script executes in the context of the user's browser, potentially leading to session hijacking, credential theft, or unauthorized actions on behalf of the user. The vulnerability is classified under CWE-79, which pertains to improper input sanitization leading to XSS. Despite the vulnerability's presence in multiple versions, the CVSS v4.0 score is low (2.0), indicating limited impact or exploitation complexity. The vector details suggest network attack vector (AV:N), low attack complexity (AC:L), but require privileges and user interaction (PR:H/UI:P), with low impact on confidentiality and integrity and no impact on availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability affects the fragment preview feature, which is used to render and preview UI components, making it a targeted attack vector for injecting malicious scripts via crafted URLs.

For European organizations using Liferay Portal or Liferay DXP, this vulnerability poses a risk primarily to web application security and user trust. Exploitation could lead to theft of session cookies, enabling attackers to impersonate legitimate users, potentially accessing sensitive data or performing unauthorized actions within the portal. This is particularly concerning for organizations that use Liferay for intranet portals, customer-facing websites, or digital experience platforms that handle personal data or business-critical information. Although the CVSS score is low, the fact that the vulnerability can be exploited remotely without authentication increases the attack surface. European organizations subject to GDPR must consider the risk of data breaches resulting from such attacks, which could lead to regulatory penalties and reputational damage. The impact is somewhat mitigated by the requirement for user interaction and privileges, but phishing or social engineering could facilitate exploitation. Additionally, the fragment preview functionality is often used by developers and content managers, so targeted attacks against these roles could disrupt business operations or lead to privilege escalation within the portal environment.

European organizations should implement the following specific mitigations: 1) Immediately audit and restrict access to the fragment preview functionality to trusted users only, minimizing exposure to untrusted or anonymous users. 2) Apply strict Content Security Policy (CSP) headers to limit the execution of unauthorized scripts within the portal context. 3) Monitor and filter incoming URLs to the fragment portlet for suspicious or malformed parameters that could carry injected scripts. 4) Educate users, especially content managers and developers, about the risks of clicking on untrusted links related to the portal. 5) Regularly update Liferay Portal and DXP to the latest versions once patches addressing CVE-2025-4599 are released. 6) Employ web application firewalls (WAFs) with custom rules to detect and block exploitation attempts targeting the fragment preview URLs. 7) Conduct internal penetration testing focusing on the fragment preview feature to identify any additional weaknesses. These measures go beyond generic advice by focusing on access control, input validation, user awareness, and proactive monitoring tailored to this specific vulnerability.