CVE-2025-46228 is a DOM-based Cross-site Scripting (XSS) vulnerability identified in the 'Event post' product developed by Bastien Ho, affecting versions up to 5.9.11. This vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. Specifically, the flaw allows untrusted user input to be processed and rendered in the Document Object Model (DOM) without adequate sanitization or encoding, enabling an attacker to inject malicious scripts that execute in the context of the victim's browser. Unlike traditional reflected or stored XSS, DOM-based XSS occurs entirely on the client side, making it harder to detect and mitigate through server-side controls alone. Exploitation typically involves tricking a user into visiting a crafted URL or interacting with manipulated page elements, which then execute the injected script. Although no known exploits are currently reported in the wild, the vulnerability poses a significant risk due to the potential for session hijacking, credential theft, unauthorized actions on behalf of the user, and distribution of malware. The absence of a patch at the time of disclosure increases the urgency for organizations to implement compensating controls. The vulnerability affects all versions of Event post up to 5.9.11, with no specific version exclusions noted. The issue was publicly disclosed on April 22, 2025, and has been enriched with CISA data, indicating recognition by cybersecurity authorities.

For European organizations, the impact of this DOM-based XSS vulnerability can be substantial, especially for entities relying on the Event post product for event management, communication, or content publishing. Successful exploitation can lead to compromise of user sessions, enabling attackers to impersonate legitimate users, access sensitive information, or perform unauthorized actions within the application. This can result in data breaches, reputational damage, and regulatory non-compliance, particularly under GDPR mandates concerning personal data protection. Additionally, attackers could leverage the vulnerability to distribute malware or conduct phishing campaigns targeting European users, amplifying the threat landscape. Given the web-based nature of the vulnerability, organizations with a large user base or those operating in sectors with high-value targets—such as finance, government, healthcare, and critical infrastructure—face elevated risks. The medium severity rating suggests moderate ease of exploitation but significant potential for impact on confidentiality and integrity of data. Availability is less likely to be directly affected, but indirect effects such as service disruption due to incident response or exploitation fallout are possible.

Implement strict input validation and output encoding on all user-controllable inputs within the Event post application, focusing on client-side scripts that manipulate the DOM. Apply Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the risk of XSS exploitation. Use security-focused JavaScript frameworks or libraries that automatically handle DOM sanitization to prevent injection of malicious code. Conduct thorough code reviews and penetration testing targeting DOM-based XSS vectors, especially for dynamic content rendering features. Educate users and administrators about the risks of clicking on suspicious links or interacting with untrusted content related to Event post. Monitor web application logs and user activity for unusual patterns that may indicate attempted exploitation. Since no patch is currently available, consider deploying Web Application Firewalls (WAFs) with custom rules to detect and block XSS payloads targeting Event post endpoints. Plan for timely updates once a vendor patch is released, ensuring rapid deployment to affected systems.