Recent developments in web technologies have seen a paradigm shift from monolithic server-based applications to REST-based microservices with feature-rich browser-based frontends. This progression has brought with it novel classes of security flaws. In this talk we review how client-side variants of injection vulnerabilities such as cross-site scripting (XSS), cross-site request forgery (CSRF) and the recently discovered client-side request hijacking, arise and how traditional defense mechanisms are ineffective. We summarize recent research in this area which shows that such issues are widespread and can have a diverse range of consequences. We go on to show how dynamic taint-tracking has proved to be an effective technique for the discovery of vulnerabilities in client-side JavaScript. The initial overhead in implementing tainting is, however, extremely high, as it typically involves delving into the inner workings of modern web browsers and JavaScript interpreters. We show how Project Foxhound (https://github.com/SAP/project-foxhound/) can help to reduce this burden by providing a flexible, open-source tool which can be fully integrated into browser automation frameworks such as Playwright. Foxhound is gaining traction in the community as the go-to tool for client-side vulnerability studies. We finish the talk by showing how Foxhound can also be used in privacy studies, an update on upcoming features, and how the community use and contribute to the project to help build a safer web! Licensed to the public under https://creativecommons.org/licenses/by-sa/4.0/ about this event: https://c3voc.de