A zero-day extensible markup language (XML) external entity (XXE) injection vulnerability in Microsoft Internet Explorer (IE) was recently disclosed by security researcher John Page. An attacker can reportedly exploit this vulnerability to steal confidential information or exfiltrate local files from the victim’s machine. Page tested the vulnerability in the latest version of IE (11) with current patches on Windows 7 and 10, and Windows Server 2012 R2 operating systems. We looked at its attack chain to better understand how the security flaw works and how it can be mitigated.