Mozilla Partially Vulnerable to Internet Explorer URL Spoofing Security Flaw

Thursday December 11th, 2003

koody wrote in to tell us that Mozilla is partially vulnerable to the recently announced URL spoofing security hole in Internet Explorer. The latest IE flaw allows an attacker to disguise the true domain of a URL in the browser's Address Bar, allowing a page located at to appear to be from This exploit can be used to increase the effectiveness of the so-called 'phishing' scams that have recently been used to target customers of PayPal, eBay and several online banks.

The Address Bar URL spoofing flaw was originally reported by Sam "Zap The Dingbat" Greenhalgh, who provided details of the exploit and a demonstration. Security company Secunia issued an advisory about the vulnerability, with an update from Chris Hall reporting that the URL shown in the Status Bar while mousing over a link to a spoofed page is also affected. While Mozilla-based browsers such as the Mozilla Application Suite and Mozilla Firebird are immune to the more serious Address Bar spoofing, they appear to be vulnerable to the Status Bar variant.

The Secunia Internet Explorer Address Bar Spoofing Test page demonstrates both the full flaw in IE and the Status Bar aspect of it that affects Mozilla. The relevant Bugzilla report is bug 228176, which was filed today and already has a preliminary patch attached (please do not add unnecessary comments to the bug; the developers are already aware of its seriousness). Mozilla users are advised to not rely on the URL displayed in the Status Bar and to check the complete address of the destination page in the Location Bar upon arrival.

#39 Status Bar is not a trusted source...

by Dizzle

Saturday December 13th, 2003 4:46 PM

You are replying to this message

The bug in Mozilla and the bug in IE are NOT of the same severity. The status bar has never been a "trusted source" of information, whether or not you turn javascript off and then believe it to be a trusted source. After you click a link the address bar will tell you the url in Mozilla and that is the source you should trust. This is why it's a huge vulnerability in IE.

Also note that if you right click on these "spoofed" url and click properties you get the correct url. So even thought this is a bug and should be fixed. It is not a security threat at all.