Plane is an open-source project management tool. Prior to 1.4.0, GET /api/v1/workspaces/{slug}/projects/{project_id}/members/ returns the complete project-member roster, including each member's email address, first and last name, display name, avatar, and role. ProjectMemberPermission gates the endpoint, but its SAFE_METHODS branch checks only whether the caller is an active ProjectMember of any project in the workspace and does not bind the check to view.project_id. The view then filters solely by the project_id supplied in the URL. Consequently, any authenticated user who belongs to one project in a workspace, including a Guest, can read the roster of another private project in the same workspace. This issue is fixed in 1.4.0.