ErrorException: Undefined index

The Zapier plugin throws an exception on line 175 of Zapier_Auth that says “Undefined index: HTTP_USER_AGENT”. This means it is possible for $_SERVER[‘HTTP_USER_AGENT’] to be undefined and therefore isset should be used. I’d recommend that line be changed to:

$is_zapier_request = isset($_SERVER['HTTP_USER_AGENT']) && $_SERVER['HTTP_USER_AGENT'] === 'Zapier' && isset($_SERVER['HTTP_X_ZAPIER_AUTH']);