<p>Using regular expressions is security-sensitive. It has led in the past to the following vulnerabilities:</p>
<ul>
  <li> <a href="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-16021">CVE-2017-16021</a> </li>
  <li> <a href="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-13863">CVE-2018-13863</a> </li>
</ul>
<p>Evaluating regular expressions against input strings is potentially an extremely CPU-intensive task. Specially crafted regular expressions such as
<code>(a+)+s</code> will take se