Coordinates of Leaflet.Draw rectangle

Leaflet.draw plugin uses standard Leaflet's L.Rectangle.

Leaflet's rectangle extends Polygon. Polygon extends Polyline.

Therefore, in order to get the coordinates of the Leaflet.draw's rectangle you can use Polyline's method getLatLngs() that returns an array of the points in the path.

Example:

var drawnItems = new L.FeatureGroup();
map.addLayer(drawnItems);

map.on('draw:created', function (e) {

    var type = e.layerType,
        layer = e.layer;

    if (type === 'rectangle') {
        layer.on('mouseover', function() {
            alert(layer.getLatLngs());    
        });
    }

    drawnItems.addLayer(layer);
});

See event object (http://leafletjs.com/reference.html#event-objects):

var map = L.map('map').setView([53.902257, 27.561640], 13);

L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png').addTo(map);

var bounds = [[53.912257, 27.581640], [53.902257, 27.561640]];

var rect = L.rectangle(bounds, {color: 'blue', weight: 1}).on('click', function (e) {
    // There event is event object
    // there e.type === 'click'
    // there e.lanlng === L.LatLng on map
    // there e.target.getLatLngs() - your rectangle coordinates
    // but e.target !== rect
    console.info(e);
}).addTo(map);

Use e.target.getLatLngs().

map.on(L.Draw.Event.CREATED, function (e) {

    var layer = e.layer;
    drawnItems.addLayer(layer);

    console.log(layer.getLatLngs())

});