CVE-2025-43781 is a reflected Cross-Site Scripting (XSS) vulnerability identified in multiple versions of Liferay Portal and Liferay DXP, specifically versions 7.4.3.110 through 7.4.3.128, and various 2024 quarterly releases of Liferay DXP (Q1.1 through Q3.8). The vulnerability arises due to improper neutralization of user-supplied input during web page generation, specifically via the URL parameter in the search bar portlet. This flaw allows remote attackers to inject arbitrary HTML or JavaScript code that is reflected back to the user without proper sanitization or encoding. When a victim accesses a crafted URL containing malicious script, the injected code executes in the context of the victim's browser session. This can lead to session hijacking, credential theft, unauthorized actions on behalf of the user, or redirection to malicious sites. The vulnerability does not require authentication and can be exploited remotely with only user interaction (clicking or visiting a malicious link). The CVSS 4.0 base score is 5.3 (medium severity), reflecting network attack vector, low attack complexity, no privileges required, but requiring user interaction and resulting in limited confidentiality and integrity impact. No known exploits are currently reported in the wild, and no official patches are linked yet. The vulnerability is categorized under CWE-79, which is a common and well-understood web application security issue.

For European organizations using Liferay Portal or Liferay DXP, this vulnerability poses a moderate risk. Liferay is widely used by enterprises, government agencies, and public sector organizations across Europe for content management and digital experience platforms. Exploitation could lead to theft of user credentials, session tokens, or sensitive information, enabling attackers to impersonate users or escalate privileges. This is particularly concerning for organizations handling personal data under GDPR, as successful attacks could lead to data breaches and regulatory penalties. Additionally, attackers could use the vulnerability to deliver malware or phishing content, undermining user trust and causing reputational damage. The reflected XSS nature means attacks require user interaction, often via social engineering, but the ease of crafting malicious URLs makes phishing campaigns plausible. The limited impact on availability reduces the risk of service disruption, but confidentiality and integrity impacts remain significant. Organizations with public-facing Liferay portals are most at risk, especially those with high user traffic or sensitive user data.

Beyond generic advice, European organizations should: 1) Immediately audit their Liferay Portal and DXP versions to identify affected instances. 2) Implement strict input validation and output encoding on all user-controllable inputs, especially URL parameters in the search bar portlet, using context-appropriate encoding (e.g., HTML entity encoding). 3) Deploy Web Application Firewalls (WAFs) with custom rules to detect and block typical XSS payload patterns targeting Liferay search URLs. 4) Educate users and administrators about phishing risks and encourage cautious behavior regarding unsolicited links. 5) Monitor web server and application logs for unusual URL patterns or spikes in suspicious requests. 6) Apply any vendor patches or updates as soon as they become available. 7) Consider isolating or disabling the vulnerable search bar portlet temporarily if patching is delayed. 8) Conduct internal penetration testing and code reviews focused on input handling in Liferay components. These targeted steps will reduce the attack surface and improve detection and response capabilities.