Project Fission - MozillaWiki

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2021-06-09 20:30:09

Fission is Mozilla's implementation of Site Isolation in Firefox. Site Isolation is a security feature that offers additional protection in case of large classes of security bugs. Site Isolation safely sandboxes web pages and web frames, isolating them from each other, further strengthening Firefox security.

Web security is designed in such a way that websites or webframes cannot access each other's data inside the browser. However, bugs happen. The Firefox teams and the Mozilla security teams invest considerable effort in avoiding security bugs, or, if they exist, finding them out and fixing them before release. However, if a bug somehow slips past developers, analysis and tests, and a sufficiently cunning attacker manages to find the bug before it can be fixed, they can sometimes craft a page specifically designed to access data from other sites that the user is currently visiting or has recently visited.

Firefox developers already employ a number of counter-measures to make such undetected bugs less likely to succeed, from programming in memory-safe languages to adopting defensive programming techniques. Site Isolation is a new counter-measure dedicated to this purpose. With Site Isolation, pages and frames are executed in processes dedicated to their origin.