CVE-2025-23850 is a high-severity reflected Cross-Site Scripting (XSS) vulnerability identified in the NotFound Mojo Under Construction plugin, affecting versions up to 1.1.2. The vulnerability arises from improper neutralization of user-supplied input during web page generation, classified under CWE-79. Specifically, the plugin fails to adequately sanitize or encode input parameters that are reflected in the HTTP response, allowing an attacker to inject malicious scripts. When a victim visits a crafted URL containing the malicious payload, the injected script executes in the context of the victim's browser, potentially leading to session hijacking, credential theft, defacement, or redirection to malicious sites. The CVSS v3.1 base score is 7.1, indicating a high severity level. The vector string (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L) shows that the attack can be launched remotely over the network without privileges, requires low attack complexity, no privileges, but does require user interaction (clicking a crafted link). The scope is changed (S:C), meaning the vulnerability affects resources beyond the vulnerable component, and it impacts confidentiality, integrity, and availability to a limited extent. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in January 2025 and published in March 2025. This reflected XSS vulnerability is typical in web applications that dynamically generate pages based on user input without proper encoding or sanitization, and it is critical to address it promptly to prevent exploitation.

For European organizations using the NotFound Mojo Under Construction plugin, this vulnerability poses a significant risk. Exploitation could allow attackers to execute arbitrary JavaScript in the context of the affected website, potentially leading to theft of user credentials, session tokens, or other sensitive information. This can result in unauthorized access to user accounts or administrative interfaces. Additionally, attackers could perform phishing attacks by injecting malicious content or redirect users to fraudulent sites, damaging organizational reputation and user trust. The reflected XSS can also be used as a pivot point for further attacks, such as delivering malware or exploiting other vulnerabilities. Given the plugin's role in displaying 'under construction' pages, it may be used on websites undergoing development or maintenance, which might have less stringent security controls, increasing risk. The impact extends to confidentiality, integrity, and availability of web services, potentially disrupting business operations and compliance with data protection regulations such as GDPR. Organizations in sectors with high web presence or customer interaction, including e-commerce, finance, and public services, are particularly vulnerable to reputational damage and regulatory penalties if exploited.

To mitigate this vulnerability, European organizations should immediately audit their use of the NotFound Mojo Under Construction plugin and identify all instances and versions deployed. Until an official patch is released, organizations should consider disabling or removing the plugin from production environments. If removal is not feasible, implement web application firewall (WAF) rules to detect and block typical reflected XSS attack patterns targeting the plugin's endpoints. Input validation and output encoding should be enforced at the application level, ensuring all user-supplied data is properly sanitized before rendering in HTML contexts. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts. Regularly monitor web server logs for suspicious requests that may indicate attempted exploitation. Additionally, educate users and administrators about the risks of clicking unknown links to reduce the likelihood of successful user interaction-based attacks. Once a patch is available from the vendor, prioritize its deployment after testing in staging environments. Finally, conduct penetration testing and vulnerability scanning focused on XSS to verify the effectiveness of mitigations.