Browser extensions are installed anywhere, they serve as an integral part of our day-to-day web routine, from AdBlockers to Auto-Translators. But - do we know what is running inside of them? Do we know what goes deep-down inside their communication routines? How do they use their internal API’s? And how do their different JS execution contexts work? In this session, I will explore these unique internal extension API’s, hidden attack-surfaces and show how these concepts can be broken & exploited using new ways! I start showing how an attacker can "jump" from one low-permissions chrome-app/extension to another, hence elevating its permissions. Then, I will show how to gain full "browser-persistency" inside extensions' background-scripts context. Chaining it all together, I show how attacker, starting from low permissions chrome-app, gains a fully-armed "extension-rootkit", a persistent JS-malware running inside of a “good” extension, along with C&C features, JS injection techniques to any tab/origin, obfuscation-techniques and more. Eventually, I will present a generic technique, targeting all chrome-users, for taking over any previously installed chrome extension and implant an "extension-rootkit" in it. REFERENCES: [1] Chrome Developers: Chrome extensions API Reference, https://developer.chrome.com/docs/extensions/reference/ [2] Chrome Developers: Chrome extensions Manfiest v2/v3 Security References, https://developer.chrome.com/docs/extensions/mv2/getstarted/ & https://developer.chrome.com/docs/extensions/mv3/security/ [3] "Websites Can Exploit Browser Extensions to Steal User Data", 2019 - https://www.securityweek.com/websites-can-exploit-browser-extensions-steal-user-data / https://www-sop.inria.fr/members/Doliere.Some/papers/empoweb.pdf [4] "Web Browser Extension User-Script XSS Vulnerabilities", 2020 - https://ieeexplore.ieee.org/document/9251185 [5] "Detecting DOM-Sourced Cross-Site Scripting in Browser Extensions", 2017 - https://ieeexplore.ieee.org/document/8094406 [6] "Attacking browser extensions", Nicolas Golubovic, 2016 - https://golubovic.net/thesis/master.pdf [7] "A Combined Static and Dynamic Analysis Approach to Detect Malicious Browser Extensions", 2018 - https://www.hindawi.com/journals/scn/2018/7087239/ [8] "Chrome Extensions: Threat Analysis and Countermeasures", 2012 - https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.374.8978&rep=rep1&type=pdf [9] "Extension Breakdown: Security Analysis of Browsers Extension Resources Control Policies", Usenix Security 2017 - https://www.usenix.org/system/files/conference/usenixsecurity17/sec17-sanchez-rola.pdf [10] "Protecting Browsers from Extension Vulnerabilities", 2010 - https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/38394.pdf