CVE-2024-9440 is a cross-site scripting (XSS) vulnerability identified in the Slim Select JavaScript library versions 2.0 through 2.9.0. The flaw exists in the select.ts file, specifically in the createOption() function, where the 'text' property from a user-provided Options object is directly assigned to the innerHTML property of a DOM element without any sanitization or encoding. This improper neutralization of input (CWE-79) allows an attacker to inject arbitrary JavaScript code that executes in the victim’s browser context when the vulnerable web application renders the malicious input. The vulnerability is remotely exploitable over the network (AV:N) with low attack complexity (AC:L), requires no privileges (PR:N), but does require user interaction (UI:R) such as clicking or viewing a crafted page. The scope is unchanged (S:U), and the impact affects confidentiality and integrity to a limited extent (C:L/I:L/A:N). No official patch is currently available, increasing the risk for applications that rely on Slim Select for dynamic list generation with unsanitized user input. While no known exploits are reported in the wild yet, the vulnerability poses a significant risk for web applications that do not implement additional input validation or output encoding. Attackers could leverage this to steal session tokens, perform actions on behalf of users, or deface web content. The vulnerability’s medium CVSS score of 5.4 reflects these factors.

For European organizations, the impact of CVE-2024-9440 centers on the potential compromise of user data confidentiality and integrity within web applications using the affected Slim Select versions. Exploitation could lead to session hijacking, unauthorized actions, or phishing attacks facilitated by injected scripts. This is particularly concerning for sectors handling sensitive personal data such as finance, healthcare, and e-commerce. Although availability is not directly impacted, the reputational damage and regulatory consequences under GDPR for data breaches involving personal data could be significant. Organizations with customer-facing web portals or internal tools that dynamically generate lists from user input are at heightened risk. The lack of an official patch necessitates immediate mitigation to prevent exploitation. Additionally, the requirement for user interaction means social engineering or phishing could be used to trigger the vulnerability. The medium severity rating suggests a moderate but actionable threat that should be addressed promptly to avoid escalation.

1. Implement strict input validation and sanitization on all user-supplied data before passing it to Slim Select, ensuring that any HTML or script tags are neutralized or removed. 2. Use output encoding libraries or frameworks that automatically escape HTML entities to prevent injection into innerHTML. 3. Where feasible, replace or upgrade Slim Select to a version that addresses this vulnerability once available, or consider alternative libraries with secure coding practices. 4. Employ Content Security Policy (CSP) headers to restrict the execution of inline scripts and reduce the impact of potential XSS attacks. 5. Conduct thorough code reviews and security testing focusing on dynamic list generation features. 6. Educate developers about secure handling of DOM manipulation and the risks of unsanitized innerHTML assignments. 7. Monitor web application logs and user reports for suspicious activity indicative of XSS exploitation attempts. 8. If immediate patching is not possible, consider disabling or limiting features that accept user input for dynamic list generation until mitigations are in place.