CVE-2025-9550 is a security vulnerability classified under CWE-79, indicating an improper neutralization of input during web page generation, commonly known as Cross-Site Scripting (XSS). This vulnerability specifically affects the Drupal Facets module, versions from 0.0.0 up to but not including 2.0.10, and from 3.0.0 up to but not including 3.0.1. The Facets module is used to create faceted search and filtering interfaces on Drupal websites, which often handle user-supplied input to dynamically generate web content. The vulnerability arises because the module fails to properly sanitize or encode user inputs before rendering them in web pages, allowing an attacker to inject malicious JavaScript code. When a victim visits a compromised page, the injected script executes in their browser context, potentially leading to session hijacking, theft of cookies or credentials, defacement, or unauthorized actions performed with the victim's privileges. Although no known exploits have been reported in the wild as of the published date, the vulnerability is publicly disclosed and thus may attract attackers. The absence of a CVSS score indicates the need for an expert severity assessment. Given the nature of XSS vulnerabilities, exploitation requires no authentication and can be triggered by user interaction (visiting a maliciously crafted page). The scope includes all Drupal sites using the affected Facets versions, which can be widespread given Drupal's popularity in Europe. The vulnerability is in a widely used open-source CMS component, increasing the risk of exploitation once proof-of-concept code becomes available. The Drupal project has not yet provided patch links, but fixed versions 2.0.10 and 3.0.1 are indicated, implying that upgrading to these versions or later will remediate the issue.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of web applications built on Drupal using the Facets module. Successful exploitation can lead to session hijacking, allowing attackers to impersonate legitimate users, including administrators, potentially resulting in unauthorized data access or modification. It can also facilitate phishing attacks by injecting deceptive content, damaging organizational reputation. Public-facing websites, especially those handling sensitive user data or providing critical services, are at heightened risk. The availability impact is generally low for XSS, but indirect effects such as site defacement or user trust erosion can have business consequences. Given Drupal's widespread use in government, education, and enterprise sectors across Europe, the vulnerability could affect a broad range of targets. The lack of known exploits currently provides a window for proactive mitigation, but the public disclosure increases the likelihood of future attacks. Organizations failing to patch or implement compensating controls may face regulatory compliance issues under GDPR if user data is compromised.

1. Immediately upgrade the Drupal Facets module to version 2.0.10 or 3.0.1, or later, as these versions contain fixes for the vulnerability. 2. Implement strict input validation and output encoding on all user-supplied data within the Drupal environment, especially in custom code interacting with Facets. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 4. Conduct thorough security testing, including automated scanning and manual code review, focusing on input handling in the Facets module and related components. 5. Monitor web server logs and application logs for unusual requests or script injection attempts targeting Facets endpoints. 6. Educate developers and administrators on secure coding practices to prevent similar vulnerabilities. 7. Consider deploying Web Application Firewalls (WAFs) with rules to detect and block XSS payloads targeting Drupal sites. 8. Regularly review and update Drupal core and contributed modules to maintain security posture. 9. For organizations with strict compliance requirements, perform a risk assessment and document mitigation efforts related to this vulnerability.