CVE-2025-66040 identifies a cross-site scripting (XSS) vulnerability in the Spotipy Python library, specifically in versions before 2.25.2. Spotipy is widely used to interact with the Spotify Web API, facilitating OAuth authentication flows. The vulnerability arises from improper neutralization of input in the OAuth callback server, where the 'error' parameter is not sanitized before being embedded in a web page. This allows an attacker to craft a malicious URL that injects JavaScript code, which executes in the context of the user's browser during OAuth authentication. The flaw is categorized under CWE-79, reflecting improper input validation leading to XSS. Exploitation requires the victim to initiate an OAuth authentication process and interact with a maliciously crafted URL, making user interaction necessary. The CVSS v3.1 score is 3.6 (low), reflecting local attack vector, high attack complexity, no privileges required, user interaction required, and limited confidentiality and integrity impact without availability impact. No known exploits are currently in the wild. The vulnerability has been addressed in Spotipy version 2.25.2 by properly sanitizing the error parameter to prevent script injection. Organizations using Spotipy in their applications should upgrade to the patched version to eliminate this risk.

For European organizations, the impact of CVE-2025-66040 is generally low but context-dependent. Since Spotipy is a developer library for Spotify API integration, the vulnerability primarily affects applications that implement OAuth authentication flows using vulnerable versions. Successful exploitation could lead to execution of arbitrary JavaScript in users' browsers, potentially enabling session hijacking, phishing, or theft of sensitive tokens during authentication. However, the attack requires user interaction and local access to the OAuth flow, limiting large-scale automated exploitation. Confidentiality and integrity of user data could be compromised in affected applications, but availability is not impacted. Organizations relying on Spotipy for internal tools or customer-facing applications should consider the risk of reputational damage and user trust erosion if exploited. The low CVSS score reflects these limited impacts, but the vulnerability should not be ignored, especially in sectors with high compliance requirements such as finance, healthcare, and public services.

To mitigate CVE-2025-66040, European organizations should immediately upgrade all Spotipy library instances to version 2.25.2 or later, where the vulnerability is patched. Developers should audit their OAuth callback implementations to ensure proper input validation and sanitization of all parameters, especially those reflected in web pages. Implement Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. Conduct security reviews and penetration testing of OAuth flows to detect any residual injection vectors. Educate developers on secure coding practices related to web input handling and OAuth integration. Monitor application logs for suspicious OAuth callback requests containing unusual or encoded script content. If upgrading is not immediately possible, consider implementing web application firewalls (WAF) rules to detect and block malicious payloads targeting the error parameter. Finally, maintain awareness of Spotipy releases and security advisories to promptly address future vulnerabilities.