CVE-2025-66306 is classified under CWE-639 (Authorization Bypass Through User-Controlled Key) and affects the Grav CMS, a popular file-based web platform used for content management. The vulnerability resides in the Admin Panel component of Grav versions before 1.8.0-beta.27. It is an IDOR flaw that allows authenticated users with low privileges to manipulate object references or keys to access sensitive information belonging to other users. Specifically, attackers can retrieve admin email addresses and other metadata that should be restricted. Although the vulnerability does not permit direct account takeover or modification of data, the leakage of sensitive metadata can facilitate secondary attacks such as phishing campaigns, credential stuffing, or social engineering. The vulnerability requires the attacker to have some level of authenticated access (low privilege) but does not require user interaction or elevated privileges. The CVSS 3.1 score is 4.3 (medium), reflecting the limited impact on confidentiality and no impact on integrity or availability. No public exploits have been reported, and the issue is resolved in Grav 1.8.0-beta.27. Organizations using Grav CMS should verify their version and apply updates accordingly to mitigate risk.

For European organizations using Grav CMS, this vulnerability poses a moderate risk primarily through the exposure of sensitive administrative metadata. The leakage of admin email addresses can lead to targeted phishing attacks, which are a common vector for initial compromise in European enterprises. Credential stuffing attacks could also be facilitated if attackers correlate exposed emails with leaked password databases. Although the vulnerability does not allow direct account takeover or system compromise, the indirect risks can lead to significant security incidents, including unauthorized access and data breaches. Organizations in sectors with high regulatory requirements for data protection (e.g., finance, healthcare, government) may face compliance risks if such metadata exposure leads to further compromise. The impact is heightened in environments where Grav CMS is used to manage critical or sensitive web content. Since exploitation requires low-privilege authenticated access, insider threats or compromised low-level accounts increase the risk profile.

1. Upgrade Grav CMS installations to version 1.8.0-beta.27 or later immediately to apply the patch that fixes this vulnerability. 2. Review and restrict user privileges in the Grav Admin Panel to the minimum necessary, limiting access to trusted users only. 3. Implement strong authentication mechanisms, such as multi-factor authentication (MFA), to reduce the risk of low-privilege account compromise. 4. Monitor access logs for unusual or unauthorized attempts to access user metadata or admin panel resources. 5. Educate administrative users about phishing and social engineering risks, especially given the potential exposure of their email addresses. 6. Consider additional application-layer access controls or web application firewalls (WAFs) that can detect and block suspicious IDOR exploitation attempts. 7. Conduct regular security audits and vulnerability scans focusing on CMS components to detect outdated versions or misconfigurations.