CVE-2025-48731 is a medium severity vulnerability identified in the Mattermost Confluence Plugin versions prior to 1.5.0. The vulnerability is classified under CWE-862, which refers to Missing Authorization. Specifically, the plugin fails to properly verify whether a user has access rights to a particular Confluence space before allowing them to edit a subscription associated with that space. This flaw exists in the 'edit subscription' endpoint of the plugin. An attacker with at least limited privileges (PR:L - privileges required) can exploit this vulnerability remotely (AV:N - network attack vector) without requiring user interaction (UI:N). The vulnerability impacts confidentiality and integrity, allowing unauthorized users to modify subscription settings for Confluence spaces they should not have access to. The CVSS v3.1 base score is 6.4, indicating a medium severity level. The scope is changed (S:C), meaning the vulnerability affects resources beyond the initially vulnerable component. The attack complexity is low (AC:L), making exploitation feasible for attackers with some level of access. There is no known exploit in the wild at the time of publication. The vulnerability does not affect availability but can lead to unauthorized information disclosure or manipulation of subscription data, potentially exposing sensitive project or organizational information managed within Confluence spaces integrated with Mattermost. No patches or fixes are listed yet, so affected organizations should monitor for updates and consider compensating controls.

For European organizations, this vulnerability poses a risk primarily to those using Mattermost integrated with Confluence for collaboration and project management. Unauthorized editing of subscriptions could lead to exposure or manipulation of sensitive information, undermining confidentiality and integrity of organizational data. This could facilitate further attacks such as social engineering, data leakage, or unauthorized access to internal communications. Given the widespread use of Confluence and Mattermost in enterprises across Europe, especially in sectors like finance, government, and technology, the impact could be significant. Organizations handling sensitive or regulated data (e.g., GDPR-protected personal data) could face compliance risks if unauthorized access leads to data breaches. The vulnerability's exploitation could also disrupt workflows and trust in collaboration tools, impacting operational efficiency.

1. Immediate mitigation should include restricting access to the Mattermost Confluence Plugin's subscription editing functionality to only highly trusted users until a patch is available. 2. Implement network-level controls such as IP whitelisting or VPN requirements to limit access to the plugin endpoints. 3. Monitor logs for unusual subscription edit activities, especially from users who should not have access to certain Confluence spaces. 4. Enforce strict role-based access controls (RBAC) within both Mattermost and Confluence to minimize privilege levels. 5. Regularly audit user permissions and subscriptions to detect unauthorized changes. 6. Stay updated with Mattermost vendor advisories and apply patches promptly once released. 7. Consider deploying Web Application Firewalls (WAF) with custom rules to detect and block suspicious requests targeting the edit subscription endpoint. 8. Educate users about the risks of unauthorized access and encourage reporting of suspicious behavior.