Open edX Platform enables the authoring and delivery of online learning at any scale. From the Ulmo release until release/ulmo.4 and release/verawood.1, the GET /api/support/v1/manage_course_team/ endpoint in CourseTeamManageAPIView requires only IsAuthenticated and omits the global support-role authorization check intended for this help-desk surface. Any authenticated learner can supply an email, username, or user_id for an arbitrary target and use the 200 and 404 response discrepancy to distinguish an active account from an absent or inactive account. A caller with a course-level or organization-level instructor role can additionally obtain the target user's staff or instructor assignments within the caller's course or organization scope. Anonymous callers remain blocked, and the separately authorized PUT behavior is outside this vulnerability. This issue is fixed in release/ulmo.4 and release/verawood.1.