CVE-2025-12126 is an authorization bypass vulnerability classified under CWE-639 (Authorization Bypass Through User-Controlled Key) found in the WordPress plugin 'The Total Book Project' by ryanmoyer. The vulnerability exists in all versions up to and including 1.0 due to insufficient validation of a user-controlled key parameter in several plugin functions. This flaw allows authenticated users with Contributor-level access or higher to perform unauthorized actions on book chapters that do not belong to them, including moving, deleting, or creating chapters. The root cause is an Insecure Direct Object Reference (IDOR), where the plugin fails to verify ownership or permission on the targeted objects before allowing modifications. The attack vector is remote and network-based, requiring authentication but no user interaction beyond login. The CVSS v3.1 base score is 5.4, indicating medium severity, with the vector string AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N, meaning the attack is remotely exploitable with low complexity, requires low privileges, no user interaction, and impacts confidentiality and integrity but not availability. No patches or exploit code are currently publicly available, and no known active exploitation has been reported. The vulnerability could be leveraged by malicious contributors or compromised accounts to alter content integrity, potentially damaging trust and data accuracy on affected WordPress sites.

For European organizations, this vulnerability poses a moderate risk primarily to the confidentiality and integrity of content managed via the affected WordPress plugin. Organizations that rely on 'The Total Book Project' plugin for managing digital books, educational content, or publishing workflows could face unauthorized content manipulation by users with Contributor-level access. This could lead to misinformation, loss of intellectual property integrity, or reputational damage if unauthorized changes are made public. While availability is not impacted, the unauthorized modification of content could disrupt workflows and require resource-intensive remediation. The risk is heightened in environments where Contributor roles are broadly assigned or where account compromise is possible. Given WordPress's widespread use across Europe, especially among SMEs, educational institutions, and publishers, the vulnerability could affect a significant number of sites if the plugin is in use. The lack of known exploits reduces immediate risk but does not eliminate the threat, especially as exploit code could emerge following public disclosure.

To mitigate this vulnerability, European organizations should first verify if 'The Total Book Project' plugin is installed and actively used on their WordPress sites. If so, immediate steps include restricting Contributor-level access to trusted users only and auditing existing Contributor accounts for suspicious activity. Since no official patch is currently available, organizations should consider disabling or uninstalling the plugin temporarily to prevent exploitation. Implementing additional access controls or custom validation checks via WordPress hooks or security plugins could help enforce ownership verification until an official fix is released. Monitoring logs for unusual chapter modification activities by Contributors can aid in early detection of exploitation attempts. Organizations should subscribe to vendor and security mailing lists for updates on patches or mitigations. Additionally, enforcing strong authentication mechanisms and regular account reviews will reduce the risk of account compromise that could facilitate exploitation.