content/browser/web_contents/web_contents_impl.cc in Google Chrome before 44.0.2403.89 does not ensure that a PDF document's modal dialog is closed upon navigation to an interstitial page, which allows remote attackers to spoof URLs via a crafted document, as demonstrated by the alert_dialog.pdf document.
Software security is not security software. Here we're concerned with topics like authentication, access control, confidentiality, cryptography, and privilege management.