This is an out-of-bound read, it's undefined behavior.

numbers only has 4 elements, that means you can only legally access index 0 to 3.

But your while loop doesn't do that bound check. Reading an element with an index outside of the array capacity will read a garbage data, if that garbage data happens to be zero, your "while loop" will stop. But that's not always the case.

IOW, you're while loop condition relies on a random undefined value.

You can just use a for loop like this to reliably stop the iteration:
int main()
{
        int numbers[]{23, 45, 76, 66};
        int i;

        for (i = 0; i < 4; i++) {
                cout << numbers[i] << endl;
        }
        return 0;
}

This is safe because it will never perform an out-of-bound read.