metamask-extension/ui/components/app/signature-request/signature-request-message/index.scss

.signature-request-message {
  flex: 1 60%;
  max-height: 231px;
  position: relative;

  &__root {
    flex: 1 100%;
    overflow: auto;

    @include screen-sm-min {
      width: auto;
    }
  }

  &__scroll-button {
    position: absolute;
    right: 28px;
    bottom: 12px;
    border-radius: 50%;
    height: 24px;
    width: 24px;
    cursor: pointer;
  }
}