So wait a sec, do you open the door to anyone without checking who is it?
Also, please note, this was just a fun small project for us. Making an image with a camera and posting to Slack would be better. We had much fun making this without putting a lot effort in it, that was for now the point.
We are aware of all the security issues and are not using this in production at our main office.
I suspect they'd be better off switching to a RFID / nfc swipe system