CVE-2026-24447 is a vulnerability in Six Apart Ltd.'s Movable Type (Software Edition) that arises from improper neutralization of formula elements in CSV files generated by the software. When malformed input data is processed by the affected versions (8.0.2 to 8.0.8, 8.8.0 to 8.8.1, and 9.0.4 to 9.0.5), the exported CSV files may contain embedded formula code. If a user downloads and opens such a CSV file in spreadsheet applications like Microsoft Excel or LibreOffice Calc, the embedded formula code can execute, potentially leading to code execution in the user's environment. This type of vulnerability is commonly referred to as CSV Injection or Formula Injection. The vulnerability affects both supported and End-of-Life versions (notably the 7 and 8.4 series are also vulnerable). The CVSS 3.0 score is 6.5, indicating medium severity, with attack vector being network-based, requiring low privileges, user interaction, and resulting in partial confidentiality, integrity, and availability impacts. No public exploits have been reported yet, but the risk exists especially in environments where CSV exports are shared and opened by users. The vulnerability is significant because CSV files are commonly used for data exchange and are often trusted by users, making this a vector for social engineering and code execution attacks.

For European organizations, this vulnerability poses a risk primarily in environments where Movable Type is used for content management and where CSV exports are routinely shared and opened by internal or external users. Successful exploitation could lead to execution of malicious code on the victim's machine, potentially allowing attackers to steal sensitive data, alter information, or disrupt operations. This is particularly concerning for organizations handling sensitive or regulated data, such as financial institutions, government agencies, and healthcare providers. The impact on confidentiality, integrity, and availability is moderate but could escalate if attackers leverage this initial foothold for further attacks. Since the vulnerability requires user interaction (opening the CSV file), phishing or social engineering campaigns could be used to increase exploitation likelihood. Additionally, the presence of vulnerable End-of-Life versions increases risk as these may not receive security updates, leaving some European organizations exposed.

1. Immediately update Movable Type installations to the latest patched versions beyond 9.0.5 or apply any vendor-provided patches addressing this vulnerability. 2. If patching is not immediately possible, implement input validation and sanitization on data that may be exported to CSV to neutralize formula characters such as '=', '+', '-', and '@' at the start of fields. 3. Educate users to be cautious when opening CSV files from untrusted or unexpected sources, especially those received via email or download links. 4. Configure spreadsheet applications to disable automatic formula execution or enable protected view modes when opening CSV files from external sources. 5. Monitor logs and user reports for suspicious CSV file downloads or unusual behavior following CSV file openings. 6. For organizations using End-of-Life versions, prioritize migration to supported versions or alternative CMS platforms to reduce exposure. 7. Implement network-level controls to restrict access to the Movable Type administrative interface to authorized personnel only, reducing the risk of malicious data injection.