Risk: Medium
A security loophole in Mozilla and Firefox browser could be used to spoof the URL displayed in the address bar, SSL certificate and status bar. The vulnerability also affects Opera and Konqueror and stems from a flawed IDN (International Domain Name) implementation within the browsers.
The bug could be exploited by registering domain names with certain international characters - which look like other commonly used characters - in order to hoodwink users into believing they are on a different, trusted site. As such, the bug creates a new wheeze for phishing attacks. For Germans to use national German characters in ".de" domains, for example, is one thing, but the use of national characters has been extended to the international domain space (.com, .net and .org) and extends the scope for confusion.
"This issue is not a traditional vulnerability, but a serious security issue which is caused by an inappropriate implementation of IDN", Secunia commented.
The "problems" involved with "o" that looks like "0" and "I" and "1", allow people to register "MICR0S0FT.COM" and abuse that to trick people. Using IDN which support Unicode characters gives phishers and scammers thousands of more characters to use, some of which resemble "normal" characters to the point where not even the trained and paranoid eye will tell the difference.
The bug has been confirmed in Mozilla 1.7.5, Firefox 1.0, Konqueror 3.2.2 and Opera 7.54. Other versions may also be affected. Internet Explorer users are in the clear from this one, although subject to flaws that have a similar effect.
The general advise is for users not to follow links from untrusted sources and to manually type in the URL they wish to visit in the address bar as a workaround prior to the availability of more comprehensive vendor patches.