CVE-2026-23547 identifies a missing authorization vulnerability in the CMSMasters Content Composer plugin, a tool used for managing and composing content within CMSMasters-based websites. The vulnerability arises from incorrectly configured access control security levels, which fail to properly verify whether a user has the necessary permissions to perform certain actions. This flaw affects all versions up to and including 2.5.8. Because authorization checks are missing or improperly implemented, an attacker could exploit this vulnerability to perform unauthorized actions such as modifying content, injecting malicious data, or escalating privileges within the CMS environment. The vulnerability does not require prior authentication, increasing the risk of exploitation. Although no public exploits have been reported yet, the flaw's nature makes it a significant risk once weaponized. The absence of a CVSS score limits precise severity quantification, but the impact on confidentiality, integrity, and potential availability of content is considerable. The vulnerability was reserved in January 2026 and published in February 2026, with no patches currently linked, indicating that organizations must proactively monitor for updates. The plugin is commonly used in CMSMasters-powered websites, which are popular among small to medium enterprises and content-heavy sites. Attackers exploiting this vulnerability could manipulate web content, deface sites, or use compromised CMS environments as a foothold for further attacks.

For European organizations, this vulnerability poses a significant risk to the integrity and confidentiality of web content managed via CMSMasters Content Composer. Unauthorized content modification could lead to misinformation, reputational damage, or the injection of malicious scripts targeting site visitors. Organizations relying on this CMS for customer-facing websites, intranet portals, or e-commerce platforms could face service disruptions or data breaches. The lack of authorization checks also increases the risk of privilege escalation, potentially allowing attackers to gain administrative control over the CMS environment. This could facilitate further lateral movement within corporate networks, exposing sensitive data or critical infrastructure. Given the widespread use of CMS platforms in Europe, particularly among SMEs and public sector websites, the vulnerability could have broad implications. Additionally, regulatory frameworks such as GDPR impose strict requirements on data protection and breach notification, increasing the legal and financial consequences of exploitation. The absence of known exploits currently provides a window for mitigation, but the threat landscape may evolve rapidly once exploit code becomes available.

European organizations should immediately audit their use of CMSMasters Content Composer and identify affected versions up to 2.5.8. Until an official patch is released, organizations should implement strict access controls at the web server and application levels, restricting plugin functionality to trusted and authenticated users only. Employing web application firewalls (WAFs) with custom rules to detect and block unauthorized requests targeting the plugin's endpoints can reduce exploitation risk. Regularly monitoring CMS logs for unusual activity or unauthorized access attempts is critical. Organizations should also isolate CMS environments from critical internal networks to limit lateral movement in case of compromise. Once patches or updates are available from CMSMasters, prompt application is essential. Additionally, organizations should educate content managers and administrators about the risks and enforce the principle of least privilege for CMS users. Conducting penetration testing focused on access control weaknesses in CMS environments can help identify residual risks. Finally, maintaining up-to-date backups of website content ensures rapid recovery if exploitation occurs.