CVE-2025-66307 identifies a user enumeration and email disclosure vulnerability in the Grav CMS admin plugin's 'Forgot Password' feature prior to version 1.11.0-beta.1. Grav is a flat-file CMS widely used for website management, and its admin plugin provides an HTML interface for configuration and content editing. The vulnerability arises because the server responses to password reset requests differ based on whether the submitted username exists, leaking information about valid usernames and their associated email addresses. This is classified under CWE-204 (Observable Response Discrepancy), where attackers can infer sensitive information by analyzing differences in server behavior. Exploiting this flaw requires no authentication or user interaction and can be performed remotely, making it accessible to a broad attacker base. While the vulnerability does not directly compromise account integrity or availability, it exposes user identity information that can be leveraged for subsequent targeted attacks such as phishing campaigns, password spraying, or social engineering. The flaw is resolved in Grav admin plugin version 1.11.0-beta.1 by standardizing responses to prevent information leakage. No known exploits are currently in the wild, but the medium CVSS score of 6.5 reflects the moderate risk posed by this information disclosure. Organizations running affected Grav versions should upgrade promptly to mitigate potential exploitation.

For European organizations, the primary impact of CVE-2025-66307 is the exposure of valid usernames and associated email addresses through the 'Forgot Password' functionality. This information leakage compromises user confidentiality and can facilitate targeted phishing attacks, increasing the risk of credential compromise and subsequent unauthorized access. While the vulnerability does not allow direct system compromise, the harvested data can be used in password spraying or social engineering campaigns, potentially leading to broader security incidents. Organizations in sectors with high-value targets such as government, education, media, and critical infrastructure may face increased risk due to the strategic value of user information. Additionally, GDPR and other privacy regulations in Europe impose strict requirements on protecting personal data, so leakage of email addresses could lead to compliance issues and reputational damage. The ease of remote exploitation without authentication increases the threat surface, especially for publicly accessible Grav admin interfaces. Overall, the vulnerability heightens the risk of targeted attacks that could escalate into more severe breaches if combined with other vulnerabilities or weak security practices.

European organizations using Grav CMS should take the following specific mitigation steps: 1) Immediately upgrade the Grav admin plugin to version 1.11.0-beta.1 or later to apply the official fix that standardizes responses and prevents user enumeration. 2) If immediate patching is not feasible, implement web application firewall (WAF) rules to detect and block suspicious 'Forgot Password' requests exhibiting enumeration patterns, such as rapid sequential attempts with different usernames. 3) Monitor logs for unusual activity around the password reset endpoint, including repeated requests from single IPs or user agents. 4) Enforce strong password policies and multi-factor authentication (MFA) for admin accounts to reduce the risk of credential compromise from phishing or password spraying. 5) Educate users and administrators about phishing risks and encourage vigilance regarding unsolicited emails referencing Grav accounts. 6) Limit exposure of the admin interface by restricting access via IP whitelisting or VPN where possible. 7) Regularly audit and review user accounts to detect and remove inactive or unnecessary users, minimizing the attack surface. These targeted actions go beyond generic advice by focusing on the specific attack vector and operational context of Grav CMS in European environments.