Jasper Mattsson is the one who discovered the Highly Critical Remote Code Execution in Drupal (SA-CORE-2018-002). The error could potentially allow attackers to exploit multiple attack vectors on a Drupal site, which could result in the site being completely compromised. Drupal 8, 7, and 6 sites could've been affected.
According to the Drupal project usage information this represents over one million sites or about 9% of sites that are running a known CMS.
After discovering it, Jasper worked with the Drupal Security Team to fix the error and make the web a safer place.