It is certainly not common. I've never seen or heard it in all my 72 years. But I'd say it means don't be careless or undesirable things will happen.

Interested in Language
Good night!
I have read an English proverb.
"At open doors dogs come in."
What does it mean? In what situations is this proverb used?
It is certainly not common. I've never seen or heard it in all my 72 years. But I'd say it means don't be careless or undesirable things will happen.
It's a new one to me too.
Among the results of my Google search: "if the doors are open, dogs can enter," that is, carelessness leads to trouble".