CVE-2025-58857 is a high-severity stored Cross-Site Scripting (XSS) vulnerability classified under CWE-79, affecting the KaizenCoders 'Table of content' product up to version 1.5.3.1. Stored XSS vulnerabilities occur when untrusted input is improperly neutralized and then stored by the application, later being rendered in web pages without adequate sanitization or encoding. This allows attackers to inject malicious scripts that execute in the context of other users' browsers. The vulnerability is remotely exploitable over the network without requiring authentication (AV:N/PR:N), but requires user interaction (UI:R) such as visiting a maliciously crafted page or content. The CVSS v3.1 base score is 7.1, reflecting a high impact on confidentiality, integrity, and availability, with a scope change (S:C) indicating that the vulnerability affects resources beyond the initially vulnerable component. Successful exploitation can lead to theft of session cookies, user impersonation, defacement, or further attacks such as privilege escalation or malware distribution. No known exploits are currently reported in the wild, and no official patches have been linked yet. The vulnerability arises from improper neutralization of input during web page generation, meaning that user-supplied data is embedded into HTML output without sufficient escaping or filtering, enabling script injection. Given the nature of stored XSS, the malicious payload persists on the server and affects all users who access the compromised content, increasing the attack surface and potential damage.

For European organizations using KaizenCoders Table of content, this vulnerability poses significant risks. Stored XSS can lead to unauthorized access to sensitive information, session hijacking, and user impersonation, undermining confidentiality and integrity of data. It can also facilitate phishing attacks or distribution of malware within corporate networks. Organizations handling personal data under GDPR could face compliance violations and reputational damage if user data is compromised. The scope change in the vulnerability suggests that exploitation could impact multiple components or users beyond the initial entry point, potentially affecting large user bases or interconnected systems. This is particularly critical for sectors such as finance, healthcare, government, and critical infrastructure in Europe, where data protection and system integrity are paramount. Additionally, the requirement for user interaction means that social engineering or targeted phishing campaigns could be used to trigger the exploit, increasing the risk of successful attacks. The absence of known exploits in the wild provides a window for proactive mitigation before widespread exploitation occurs.

European organizations should prioritize the following specific mitigation steps: 1) Immediately audit all instances of KaizenCoders Table of content for usage and version to identify affected deployments. 2) Apply any available patches or updates from KaizenCoders as soon as they are released. In the absence of official patches, implement temporary mitigations such as input validation and output encoding on all user-supplied data fields involved in the Table of content rendering process. 3) Employ Content Security Policy (CSP) headers to restrict execution of unauthorized scripts and reduce the impact of XSS payloads. 4) Conduct thorough code reviews and penetration testing focused on input handling and output encoding to detect and remediate similar issues. 5) Educate users and administrators about the risks of clicking on untrusted links or content that could trigger stored XSS attacks. 6) Monitor web application logs and user reports for suspicious activity indicative of exploitation attempts. 7) Consider deploying Web Application Firewalls (WAFs) with rules tailored to detect and block XSS attack patterns targeting the affected product. These measures, combined, will reduce the attack surface and mitigate the risk until a permanent fix is applied.