This indicates an attack attempt to exploit a Denial of Service vulnerability in Drupal Module SVG Sanitizer.
The vulnerability is due to an error when the vulnerable software handles a maliciously crafted request. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
Drupal Module SVG Sanitizer 8.x-1.0-alpha1 and below
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.