Cross-site scripting (XSS) vulnerability in the Simple Subscription module before 6.x-1.1 and 7.x-1.x before 7.x-1.1 for Drupal allows remote authenticated users with the "administer blocks" permission to inject arbitrary web script or HTML via vectors related to block content.
https://www.drupal.org/node/2446019
https://www.drupal.org/node/2437933
https://www.drupal.org/node/2437931