The vulnerability is an Insecure Direct Object Reference (IDOR) in the updateUserNotifications endpoint of StudioCMS. Any authenticated visitor can supply a target user ID in the request payload and modify that user’s notification preferences, even if the target user is different from the requestor. This allows an attacker to disable or alter notifications for any account, including administrators, thereby suppressing alerts and possibly hiding malicious activity. The weakness is identified as CWE‑639.

The issue affects the StudioCMS product from withstudiocms, specifically any release prior to 0.4.3. Users running versions earlier than 0.4.3 are vulnerable.

The CVSS score of 5.4 classifies the flaw as moderate. However, its EPSS score of less than 1% suggests that, historically, this type of IDOR has rarely been exploited in the wild. The vulnerability is not designated as a Known Exploited Vulnerability by CISA. Attack vector is internal/knowledge of an authenticated session; an attacker needs only a valid user session to manipulate another user's settings. Because the flaw allows modification of notification preferences—including disabling admin alerts—it can compromise detection of malicious activity but does not directly grant code execution or broad system compromise.