CVE-2025-43818 is a medium-severity Cross-Site Scripting (XSS) vulnerability identified in the Calendar widget of Liferay Portal versions 7.4.3.35 through 7.4.3.110, as well as multiple versions of Liferay DXP (2023.Q4.0 through 2023.Q4.4, 2023.Q3.1 through 2023.Q3.6, 7.4 update 35 through update 92, and 7.3 update 25 through update 36). The vulnerability arises from insufficient input sanitization or output encoding of the “Name” text field within the Calendar widget, allowing remote attackers to inject arbitrary web scripts or HTML. This injection can be exploited by crafting a malicious payload that, when rendered by a victim's browser, executes attacker-controlled scripts. The CVSS 4.0 vector indicates the attack is network exploitable (AV:N), requires low attack complexity (AC:L), no privileges (PR:L) but user interaction (UI:A), and results in low confidentiality and integrity impact (VC:L, VI:L), with no availability impact. The vulnerability does not require authentication but does require the victim to interact with the malicious content, such as viewing a compromised calendar entry. While no known exploits are currently in the wild, the presence of this vulnerability in widely used Liferay Portal and DXP versions poses a risk of targeted phishing or session hijacking attacks. The vulnerability is categorized under CWE-79, a common XSS weakness, which can lead to theft of session cookies, defacement, or redirection to malicious sites. No official patches or mitigation links are provided yet, indicating the need for immediate attention by administrators to monitor and apply vendor updates once available.

For European organizations using Liferay Portal or DXP, this vulnerability can lead to significant security risks, especially in sectors relying on portal-based collaboration and content management such as government, finance, healthcare, and education. Successful exploitation could allow attackers to execute scripts in the context of authenticated users, potentially leading to session hijacking, unauthorized actions, or data theft. Given the interactive nature of the vulnerability (requiring user interaction), phishing campaigns could be tailored to exploit this flaw, increasing the risk of credential compromise or lateral movement within networks. The impact on confidentiality and integrity, while rated low to medium, can be amplified in environments where sensitive data or critical business processes are managed via Liferay portals. Additionally, the widespread use of Liferay in European public sector and enterprises means that exploitation could undermine trust in digital services and cause reputational damage. Although availability is not directly affected, the indirect consequences of compromised user accounts or injected malicious content could disrupt business operations and compliance with data protection regulations such as GDPR.

Organizations should immediately audit their Liferay Portal and DXP deployments to identify affected versions. Until official patches are released, administrators should implement strict input validation and output encoding on the Calendar widget’s “Name” field, potentially via custom filters or web application firewalls (WAFs) configured to detect and block suspicious script payloads. User awareness training should be enhanced to recognize phishing attempts that might leverage this vulnerability. Restricting user permissions to limit who can create or edit calendar entries can reduce the attack surface. Monitoring logs for unusual activity related to calendar modifications or unexpected script injections is recommended. Once vendor patches become available, prompt application is critical. Additionally, organizations should consider deploying Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the portal environment. Regular security assessments and penetration testing focusing on web application input handling will help detect similar vulnerabilities proactively.