CVE-2025-61950 is a medium-severity authorization bypass vulnerability affecting multiple versions of Japan Total System Co.,Ltd.'s GroupSession collaboration software products, specifically the Free edition prior to version 5.3.0, byCloud prior to 5.3.3, and ZION prior to 5.3.2. The vulnerability arises from improper implementation of authorization checks on the memo field of Circular notices, which are designed to be non-editable once created. An authenticated user with legitimate access can craft a specially formed request to bypass these checks and alter the memo field content. This flaw compromises the integrity of the data within the collaboration platform, potentially leading to misinformation, unauthorized content changes, or manipulation of official notices. The vulnerability does not affect confidentiality or availability directly and requires the attacker to have at least some level of authenticated access (privilege required: low). No user interaction beyond authentication is necessary, and the attack can be executed remotely over the network (attack vector: network). The CVSS vector (CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N) reflects these characteristics. Although no known exploits are currently reported, the vulnerability poses a risk to organizations relying on GroupSession for internal communications and document circulation. The lack of patch links suggests that users should monitor vendor advisories for updates or apply available patches promptly once released.

For European organizations, this vulnerability could undermine the integrity of internal communications and document workflows managed through GroupSession products. Unauthorized modification of Circular notices' memo fields may lead to misinformation, miscommunication, or manipulation of official records, potentially affecting decision-making processes and compliance with regulatory requirements. While the vulnerability does not expose sensitive data or disrupt service availability, the integrity compromise could damage organizational trust and operational reliability. Sectors such as government agencies, healthcare, finance, and large enterprises that utilize GroupSession for collaboration and document circulation are particularly at risk. The medium severity rating indicates that while the threat is not critical, it should not be overlooked, especially in environments where data integrity is paramount. The absence of known exploits reduces immediate risk but does not preclude future exploitation attempts. Organizations failing to update may face targeted attacks exploiting this flaw to alter official communications or internal notices.

1. Upgrade affected GroupSession products to the latest patched versions: Free edition to version 5.3.0 or later, byCloud to 5.3.3 or later, and ZION to 5.3.2 or later as soon as they become available. 2. Until patches are applied, restrict user privileges to the minimum necessary, especially limiting the ability to create or modify Circular notices. 3. Implement monitoring and logging of changes to Circular notices and memo fields to detect unauthorized modifications promptly. 4. Conduct regular audits of user permissions and access controls within GroupSession to ensure only authorized personnel can perform sensitive actions. 5. Educate users about the risk of unauthorized data modification and encourage reporting of suspicious activity. 6. Coordinate with the vendor for timely security updates and advisories. 7. Consider network segmentation or additional access controls to limit exposure of GroupSession servers to untrusted networks. 8. Review and enhance incident response plans to address potential integrity breaches in collaboration platforms.