I got this hacs/subscribe error message

I got this error message which unsure why? Anyone have any idea?

Logger: homeassistant.components.websocket_api.http.connection
Source: components/websocket_api/connection.py:96
Integration: Home Assistant WebSocket API (documentation, issues)
First occurred: 9:36:23 PM (4 occurrences)
Last logged: 9:36:23 PM

[140659282621680] Received invalid command: hacs/subscribe

Same here. Wonder if no one knows about it as it maybe doesn’t present thru the GUI?