CVE-2025-43818 is a cross-site scripting (XSS) vulnerability identified in the Calendar widget of Liferay Portal versions 7.4.3.35 through 7.4.3.110 and multiple Liferay DXP releases from 2023.Q3.1 through 2023.Q4.4, including various update versions of 7.3 and 7.4. The vulnerability arises from insufficient sanitization of user input in the Calendar's “Name” text field, enabling remote attackers to inject arbitrary JavaScript or HTML code. This injection can be triggered by crafting a malicious payload submitted to the vulnerable field, which is then rendered unsafely in the web interface. The vulnerability is classified under CWE-79, indicating a classic reflected or stored XSS issue. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:L), user interaction required (UI:A), and low impact on confidentiality, integrity, and availability (VC:L, VI:L, VA:N). No authentication is strictly required, but some privileges may be needed to access the Calendar widget. Exploitation could allow attackers to execute scripts in the context of the victim’s browser, potentially stealing session tokens, manipulating page content, or redirecting users to malicious sites. Although no known exploits are reported in the wild, the vulnerability poses a risk to organizations using affected Liferay versions, especially those exposing the Calendar widget to external users or employees. The lack of available patches at the time of reporting necessitates interim mitigations such as input validation and output encoding. The vulnerability affects a widely used enterprise portal platform, which is popular in various sectors including government, finance, and education across Europe.

For European organizations, this vulnerability could lead to unauthorized disclosure of sensitive information, session hijacking, and potential compromise of user accounts through malicious script execution. Organizations relying on Liferay Portal for internal collaboration or public-facing services may face reputational damage, data leakage, or disruption of services if attackers exploit this XSS flaw. The impact is particularly significant for sectors handling sensitive personal data or critical infrastructure, where trust and data integrity are paramount. Since the vulnerability requires user interaction, phishing or social engineering campaigns could be used to lure users into triggering the malicious payload. The medium CVSS score reflects moderate risk, but the widespread use of Liferay in Europe increases the potential attack surface. Additionally, attackers could leverage this vulnerability as a foothold for further attacks within the network, especially in environments where Liferay integrates with other enterprise systems. The absence of known exploits suggests a window of opportunity for defenders to remediate before active exploitation occurs.

1. Monitor Liferay’s official channels for patches addressing CVE-2025-43818 and apply them promptly once available. 2. Implement strict input validation on the Calendar widget’s “Name” field to reject or sanitize suspicious characters and scripts. 3. Apply robust output encoding/escaping techniques on all user-supplied content rendered in the Calendar widget to prevent script execution. 4. Restrict access to the Calendar widget to authenticated and authorized users only, minimizing exposure. 5. Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in browsers. 6. Conduct user awareness training to reduce the risk of social engineering attacks that could trigger the vulnerability. 7. Regularly audit and monitor web application logs for unusual input patterns or error messages related to the Calendar widget. 8. Consider deploying Web Application Firewalls (WAF) with custom rules to detect and block XSS payloads targeting the Calendar widget. 9. Review and harden the overall Liferay Portal configuration to minimize attack surface and privilege escalation opportunities. 10. Test the environment after mitigation to ensure the vulnerability is effectively addressed.