The remote Debian host is missing a security-related update.
A remote code execution vulnerability has been found in Drupal, a fully-featured content management framework. For additional information, please refer to the upstream advisory at https://www.drupal.org/sa-core-2018-004
Upgrade the drupal7 packages. For the oldstable distribution (jessie), this problem has been fixed in version 7.32-1+deb8u12. For the stable distribution (stretch), this problem has been fixed in version 7.52-2+deb9u4.