CVE-2025-31687 is a Cross-Site Scripting (XSS) vulnerability identified in the SpamSpan filter component of Drupal, a widely used open-source content management system (CMS). The vulnerability arises from improper neutralization of input during web page generation, specifically within the SpamSpan filter versions prior to 3.2.1. This filter is designed to obfuscate email addresses to prevent spam but fails to adequately sanitize user-supplied input, allowing malicious actors to inject and execute arbitrary scripts in the context of a victim's browser. The vulnerability is classified under CWE-79, which pertains to improper input validation leading to XSS attacks. The CVSS 3.1 base score is 6.1 (medium severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The scope is changed (S:C), meaning the vulnerability can affect resources beyond the initially vulnerable component. The impact metrics indicate low confidentiality and integrity impacts (C:L/I:L) and no impact on availability (A:N). No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was published on March 31, 2025, and affects SpamSpan filter versions before 3.2.1, including version 0.0.0 as listed. Given Drupal's extensive use in web applications, this vulnerability could be exploited by attackers to execute malicious scripts, potentially leading to session hijacking, defacement, or redirection to malicious sites, especially if users interact with crafted content containing the malicious payload.

For European organizations utilizing Drupal CMS with the SpamSpan filter component, this vulnerability poses a moderate risk. Successful exploitation could lead to the compromise of user sessions, theft of sensitive information, or manipulation of web content, impacting the confidentiality and integrity of data. While availability is not directly affected, the reputational damage and potential regulatory consequences under GDPR for data breaches could be significant. Organizations in sectors with high web presence such as government, finance, healthcare, and e-commerce are particularly at risk due to the potential for targeted phishing or social engineering attacks leveraging this XSS flaw. The requirement for user interaction means that phishing campaigns or malicious links embedded in emails or websites could be vectors for exploitation. The changed scope indicates that the vulnerability could affect other components or users beyond the immediate application, increasing the potential impact. Given Drupal's popularity in Europe, especially in public sector websites and digital services, the threat could disrupt trust and service integrity if exploited.

1. Immediate upgrade of the SpamSpan filter to version 3.2.1 or later once available, as this version addresses the vulnerability. 2. Implement Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of XSS attacks. 3. Employ rigorous input validation and output encoding in custom Drupal modules or themes that interact with the SpamSpan filter to prevent injection of malicious scripts. 4. Conduct regular security audits and penetration testing focusing on web application vulnerabilities, particularly XSS. 5. Educate end-users and administrators about the risks of clicking on suspicious links or interacting with untrusted content to mitigate user interaction requirements. 6. Monitor web server and application logs for unusual activity that may indicate exploitation attempts. 7. Utilize web application firewalls (WAFs) configured to detect and block XSS attack patterns targeting Drupal components. 8. For organizations unable to immediately patch, consider disabling the SpamSpan filter temporarily if feasible, or restrict its usage to trusted content only.