Enlarge (credit: Torkild Retvedt) Attackers are mass-exploiting a recently fixed vulnerability in the Drupal content management system that allows them to take complete control of powerful website servers, researchers from multiple security companies are warning. At least three different attack groups are exploiting "Drupalgeddon2," the name given to an extremely critical vulnerability Drupal maintainers patched in late March, researchers with Netlab 360 said Friday.