CrossFire: An Analysis of Firefox Extension-Reuse Vulnerabilities

Extension architectures of popular web browsers have been carefully studied by the research community; however, the security impact of interactions between different extensions installed on a given system has received comparatively little attention. In this paper, we consider the impact of the lack of isolation between traditional Firefox browser extensions, and identify a novel extension-reuse vulnerability that allows adversaries to launch stealthy attacks against users. This attack leverages capability leaks from legitimate extensions to avoid the inclusion of security-sensitive API calls within the malicious extension itself, rendering extensions that use this technique difficult to detect through the manual vetting process that underpins the security of the Firefox extension ecosystem.