Running user JavaScript safely in the browser demands layered isolation, strict CSP design, careful message handling, and relentless testing. This article explains how sandboxed iframes, Web Workers, and security checks work together to contain custom code without exposing secrets. #websecurity #javascript #csp #cybersecurity #securecoding #webdevelopment

Giving users a way to execute custom JavaScript inside a web app sounds useful right up until you think about what those users paste into the page. Tokens, API keys, JWTs, production payloads, internal JSON, and debugging data often show up in browser tools. That makes