Version 1.6.0 – 1.6.2 are affected. I get this PHP error where the widget is located:
Warning: Invalid argument supplied for foreach() in /home/public_html/wp-content/plugins/popular-widget/_inc/functions.php on line 389
Warning: Invalid argument supplied for foreach() in /home/public_html/wp-content/plugins/popular-widget/_inc/functions.php on line 389
Had to revert back to 1.5.9 to fix.