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.

#12 Re: Mozilla Firebird 0.7

by ehrbar

Thursday December 11th, 2003 11:38 PM

You are replying to this message

<i>Unsavvy web surfers could easily mistaken this to be a real page under the official URL when in fact it is not.</i>

Yeah, but that's always been true, for all browsers. @-spoofing is something users have to be educated about, of course, but it isn't anything new.

What's tricky about this one in IE is, when you go to the destination page, you only see the spoofed URL, not anything after it. With the unprintable character, IE hides the malicious domain. User education is not enough; they would have to check the page source for the link before clicking on a link to be sure it's legit. <i>That's</i> a major problem.