Reverse Tabnapping
Overview
When an <a> tag uses target="_blank" without rel="noopener noreferrer", the opened page gets a reference to the opener window via window.opener. A malicious opened page can redirect the original tab to a phishing page (window.opener.location = 'https://phishing.com').
Remediation
Always add rel="noopener noreferrer" to links with target="_blank":
Vulnerable:
<a href="https://external.com" target="_blank">Visit</a>
Safe:
<a href="https://external.com" target="_blank" rel="noopener noreferrer">Visit</a>