function blockCmdArrowNavigation() {
			if (Env.mac) {
				editor.on('keydown', function(e) {
					if (VK.metaKeyPressed(e) && !e.shiftKey && (e.keyCode == 37 || e.keyCode == 39)) {
						e.preventDefault();
						editor.selection.getSel().modify('move', e.keyCode == 37 ? 'backward' : 'forward', 'lineboundary');
					}
				});
			}
		}
Firefox on Mac OS will move the browser back to the previous page if you press CMD+Left arrow.
You might then loose all your work so we need to block that behavior and replace it with our own.