Improper Check for Unusual or Exceptional Conditions
lettersanitizer is a DOM-based HTML email sanitizer for in-browser email rendering. All versions of lettersanitizer below 1.0.2 are affected by a denial of service issue when processing a CSS at-rule `@keyframes`. This package is depended on by react-letter
https://github.com/mat-sz/react-letter, therefore everyone using react-letter is also at risk. The problem has been patched in version 1.0.2.