<div class="cp_card">
コンテンツ
  <div class="cp_ribbon08_2">
    <div class="cp_ribbon">Ribbon</div>
  </div>
</div>

.cp_card {
  position: relative;/*リボンをかけたいコンテンツボックスにセット*/
  width: 300px;
  height: 300px;
  background: #ffffff;
  margin: auto;
  padding: 5px;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
}
/*リボンの位置*/
.cp_ribbon08_2 {
  position: absolute;
  top: 20px;
  left: -8px;
}
/*リボン内のテキスト*/
.cp_ribbon08_2 .cp_ribbon {
  position: relative;
  display: flex;
  align-items: center;
  width: 100%;
  height: 40px;
  padding: 0 5px 0 10px;
  color: #ffffff;
  background: #4CAF50;
  clip-path: polygon(0% 0%, 85% 0%, 100% 50%, 85% 100%, 0% 100%);
}
.cp_ribbon08_2:before {/*リボンの影部分*/
  position: absolute;
  content: '';
  top: -8px;
  left: 0;
  width: 8px;
  height: 8px;
  background-color: #2E7D32;
  clip-path: polygon(100% 0, 0% 100%, 100% 100%);
}