xiaoheiFS Vulnerable to RCE via Arbitrary Payment Plugin Upload (Automatic Execution)

xiaoheiFS is a self-hosted financial and operational system for cloud service businesses. In versions up to and including 0.3.15, the `AdminPaymentPluginUpload` endpoint lets admins upload any file to `plugins/payment/`. It only checks a hardcoded password (`qweasd123456`) and ignores file content. A background watcher (`StartWatcher`) then scans this folder every 5 seconds. If it finds a new executable, it runs it immediately, resulting in RCE. Version 4.0.0 fixes the issue.