Location bar and SSL indicator spoofing via window.open() on invalid URL — Mozilla

Security researcher Juan Pablo Lopez Yacubian reported that an attacker could call window.open() on an invalid URL which looks similar to a legitimate URL and then use document.write() to place content within the new document, appearing to have come from the spoofed location. Additionally, if the spoofed document was created by a document with a valid SSL certificate, the SSL indicators would be carried over into the spoofed document. An attacker could use these issues to display misleading location and SSL information for a malicious web page.