Content Security Policy has been around for 10 years and still only a fraction of sites on the Web leverage its full potential to mitigate XSS and other flaws. In this talk, we will analyze the evolution of CSP over time and how sites could leverage it to secure against three attacks classes. This is based on our NDSS 2020 paper (https://swag.cispa.saarland/papers/roth2020csp.pdf), which sheds light on the usage of CSP on 10,000 sites over a period of six years. Furthermore, we discuss insights on technical roadblocks of CSP (NDSS 2021, https://swag.cispa.saarland/papers/steffens2021blockparty.pdf), which shows that CSP’s success is in large parts blocked by third parties. Finally, we will discuss our most recent work on (un)usability aspects and fundamental roadblocks for developers (CCS 2021, https://swag.cispa.saarland/papers/roth2021usable.pdf).