Input validation vulnerability in PhpList Subber 1.1

The plugin called PhpList Subber, which is used with WordPress, has a security issue that allows unauthorized individuals to make changes to subscription forms. This vulnerability affects all versions of the plugin up to version 1.1. It occurs because the plugin does not properly check for a security code (called a nonce) when handling bulk actions. This means that if a hacker can trick a site administrator into clicking on a link, they can use a fake request to synchronize a large number of subscription forms.