Hardening the Firefox Front End with Content Security Policies
Published on: 2025-05-07 17:34:16
Most of the Firefox User Interface (UI), including the address bar and the tab strip, are implemented using standard web technologies like HTML, CSS and JavaScript plus some additional custom components like XUL. One of the advantages of using web technologies for the front end is that it allows rendering the frontend using the browser engine on all desktop operating systems. However, just like many web applications are susceptible to some form of injection attack (OWASP Top Ten), Firefox’s use of web technologies for the frontend makes it no exception and hence it is vulnerable to injection attacks as well.
The most well known type of injection attack are Cross-Site Scripting (XSS) attacks. Like the name suggests, these attacks violate the boundary between different sites and circumvent first line security defenses like the same-origin policy. As with the existence of boundaries between different sites, the Firefox UI, which runs in the parent process, is separated from web content r
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