On Nov. 27, Mozilla released the newest, security-patched version of the popular Web browser, Firefox 18.104.22.168.
The vast majority of Firefox users will have the latest and greatest automatically installed on their systems. This latest update includes fixes for three security bugs.
Perhaps the most important of these fixes is one that prevents an XSS (Cross-Site Scripting) attack. This particular XSS fix prevents the "jar: URI" hazard, which is a mechanism that had been designed to support digitally signed Web pages.
This in turn enabled Web administrators to set up sites that could load pages that had been packaged in .zip archives containing signatures in Java archive format. The problem was that Firefox couldnt identify the true source of the jar: content.
Heres how it might work in practice. Many Web 2.0 applications allow the upload of jar/.zip files. For example, Web mail clients, collaboration systems and document sharing systems all allow such uploads. You see such popular document formats as OpenWriters .odt (OpenDocument Text) and Microsoft Office 2007 Open XML use the .zip format to space.
Youre probably beginning to see where this goes. All an attacker need do is create a document in one of those formats, change its extension to .zip and, ta-da, instant Trojan horse.
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