CVE-2026-55502: Cloudreve OAuth Admin.Read scope can update OneDrive storage policy credentials

Cloudreve 4.16.1 has an OAuth scope authorization bypass in the admin storage policy routes. An OAuth bearer token scoped to Admin.Read but not Admin.Write can call POST /api/v4/admin/policy/oauth/signin and update OneDrive storage policy credentials.

The route is inside the admin group that requires Admin.Read, but it does not add the local Admin.Write guard used by sibling policy mutation routes. Its handler persists attacker-supplied secret and app_id values into the selected OneDrive storage policy before returning an OAuth URL.