CVE-2025-43757 is a reflected Cross-Site Scripting (XSS) vulnerability identified in multiple versions of the Liferay Portal and Liferay DXP products, specifically affecting versions 7.4.0 through 7.4.3.132 and various quarterly releases from 2024.Q1 through 2025.Q2. This vulnerability arises due to improper sanitization of user-supplied input in the _com_liferay_dynamic_data_mapping_web_portlet_DDMPortlet_definition parameter. An authenticated remote attacker can exploit this flaw by injecting malicious JavaScript code that is reflected back in the web application response. The vulnerability is classified under CWE-79, which pertains to improper neutralization of input during web page generation, leading to XSS attacks. The CVSS 4.0 base score is 4.8 (medium severity), with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:H indicates high privileges required, but the vector states PR:H, meaning privileges are required), and user interaction is required (UI:P). The vulnerability impacts confidentiality to a low degree but does not affect integrity or availability. There are no known exploits in the wild at the time of publication, and no official patches have been linked yet. The vulnerability requires the attacker to be authenticated, which limits the attack surface to users with valid credentials, but the presence of reflected XSS can still facilitate session hijacking, phishing, or other client-side attacks within the context of the authenticated user session.

For European organizations using Liferay Portal or Liferay DXP, this vulnerability poses a moderate risk primarily to web application security and user session integrity. Exploitation could allow attackers to execute arbitrary JavaScript in the context of authenticated users, potentially leading to session hijacking, theft of sensitive information, or unauthorized actions performed on behalf of the user. This could impact internal portals, customer-facing web applications, or intranet services relying on Liferay, thereby affecting confidentiality and trust. The requirement for authentication reduces the risk of widespread exploitation but does not eliminate the threat, especially in environments with many users or where privilege escalation is possible. Given Liferay's popularity among European enterprises for content management and digital experience platforms, the vulnerability could disrupt business operations, lead to data leakage, or damage organizational reputation if exploited. The absence of known exploits in the wild suggests that immediate risk is moderate, but organizations should act proactively to prevent potential attacks.

European organizations should implement the following specific mitigations: 1) Immediately audit and restrict user privileges to minimize the number of users with access to vulnerable Liferay versions, reducing the pool of potential attackers. 2) Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious payloads targeting the _com_liferay_dynamic_data_mapping_web_portlet_DDMPortlet_definition parameter. 3) Conduct thorough input validation and output encoding on all user-supplied data within custom Liferay portlets or extensions to prevent injection of malicious scripts. 4) Monitor logs for unusual activity or repeated attempts to exploit this parameter, focusing on authenticated user sessions. 5) Engage with Liferay support or community channels to obtain patches or updates as soon as they become available and prioritize their deployment in test and production environments. 6) Educate users about phishing and social engineering risks that could leverage XSS vulnerabilities to escalate attacks. 7) Consider isolating or segmenting Liferay Portal instances to limit lateral movement if exploitation occurs.