A security researcher has demonstrated how it is still possible to silently install extensions, or as Mozilla calls them add-ons, for the open source Firefox web browser. In a blog post, Julian Sobrier of ZScaler detailed the process, which makes use of the fact that Firefox uses an Sqlite3 database to maintain information about which add-ons are installed and, of those, which ones have been approved by the user.
This feature, introduced in Firefox 8, was designed to stop toolbars and other applications adding in their own add-ons without informing the user. Sobrier's technique shows though that the mechanism is relatively easy to overcome. Add-ons have privileged access to the browser and therefore a malicious add-on could do anything including stealing the user's history, modifying pages' contents or disabling security features in the browser.
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