CVE-2025-43815 is a reflected Cross-Site Scripting (XSS) vulnerability identified in specific versions of the Liferay Portal product, namely versions 7.4.3.102 through 7.4.3.110, and Liferay DXP versions 2023.Q4.0 through 2023.Q4.2, and 2023.Q3.5. The vulnerability arises from improper neutralization of input during web page generation, specifically on the page configuration page. The flaw is triggered via the 'com_liferay_layout_admin_web_portlet_GroupPagesPortlet_backURLTitle' parameter, which allows remote attackers to inject arbitrary web scripts or HTML code. This injection occurs because the input is not sufficiently sanitized or encoded before being reflected back in the web page, enabling malicious payloads to execute in the context of the victim's browser. The vulnerability is classified under CWE-79, which covers improper neutralization of input leading to XSS attacks. According to the CVSS v4.0 scoring, the vulnerability has a base score of 5.1 (medium severity), with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requires user interaction (UI:A). The impact on confidentiality and integrity is low, with no impact on availability. No known exploits are reported in the wild as of the publication date (September 29, 2025), and no official patches have been linked yet. The vulnerability allows attackers to craft malicious URLs or requests that, when visited or triggered by users with access to the affected Liferay Portal pages, can execute arbitrary scripts, potentially leading to session hijacking, phishing, or other client-side attacks.

For European organizations using the affected versions of Liferay Portal or Liferay DXP, this vulnerability poses a moderate risk primarily to the confidentiality and integrity of user sessions and data accessed via the portal. Liferay Portal is widely used in enterprise environments, including government, education, and private sectors, for content management and collaboration. Exploitation could allow attackers to steal session cookies, perform actions on behalf of authenticated users, or deliver malicious payloads to users within the organization. This could lead to unauthorized access to sensitive information, reputational damage, and potential compliance violations under GDPR if personal data is compromised. Since the attack requires user interaction, the risk is somewhat mitigated by user awareness and security controls, but phishing campaigns or social engineering could increase exploitation likelihood. The reflected XSS could also be leveraged as a stepping stone for more advanced attacks, such as privilege escalation or lateral movement within the network if combined with other vulnerabilities or misconfigurations.

1. Immediate mitigation should include implementing strict input validation and output encoding on the 'com_liferay_layout_admin_web_portlet_GroupPagesPortlet_backURLTitle' parameter to neutralize any injected scripts. 2. Organizations should monitor for updates or patches from Liferay and apply them promptly once available. 3. Employ Web Application Firewalls (WAFs) configured to detect and block reflected XSS payloads targeting Liferay Portal endpoints. 4. Conduct user awareness training focusing on recognizing phishing attempts and suspicious links to reduce the risk of user interaction with malicious payloads. 5. Implement Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers accessing the portal. 6. Regularly audit and review portal configurations and access controls to minimize exposure. 7. Use security scanning tools to detect XSS vulnerabilities proactively in web applications. 8. Consider isolating the Liferay Portal environment or restricting access to trusted networks to reduce exposure to external threats.