Javascript

Ghost embeds are easy to drop into a page and easy to forget from a CSP perspective. That’s where people get burned: the embed works in development, then production CSP blocks it, or worse, someone loosens the policy with script-src * and calls it done. Don’t do that. If you’re embedding Ghost content, membership widgets, or Portal-related UI on your site, you need to explicitly allow the right sources and keep the policy tight everywhere else. The good news is Ghost’s embed surface is pretty manageable if you approach it methodically. ...

Plotly.js is great until you put a real Content Security Policy in front of it. I’ve seen this go the same way a bunch of times: charts work fine in local dev, someone adds a decent CSP in staging, and suddenly the graph is blank, console errors pile up, and the quick “fix” is to throw 'unsafe-inline' and 'unsafe-eval' into the policy. That usually gets the chart rendering again, but it also guts the point of having CSP. ...

Leaflet looks simple until you lock down your site with Content Security Policy. Then the map goes blank, markers disappear, plugin styles break, and you end up staring at DevTools wondering why a harmless map library suddenly needs half the internet. I’ve hit this enough times that I treat Leaflet as a CSP integration task, not just a UI widget. The good news: most failures come from a handful of repeat mistakes. ...

PDF.js is one of those libraries that looks simple until CSP gets involved. You drop in the viewer, load a PDF, and everything works locally. Then you turn on a real Content Security Policy and suddenly the worker fails, fonts disappear, images stop rendering, or the whole viewer goes blank with a useless console error. I’ve hit this a few times. The pattern is usually the same: people start with a generic CSP, then keep adding exceptions until the app works again. That usually ends with unsafe-inline, unsafe-eval, and a policy that technically exists but doesn’t really protect anything. ...

ApexCharts is one of those libraries that looks harmless until you turn on a strict Content Security Policy and parts of your charts suddenly stop rendering. I’ve hit this a few times in dashboards where everything worked fine locally, then failed in staging because CSP blocked inline styles or scripts. ApexCharts itself is pretty friendly compared to some older charting libraries, but you still need to account for how it injects styles and how your app loads it. ...

Google Maps is one of those integrations that looks trivial right up until CSP starts blocking half of it. I’ve seen this play out a few times: the site already has a decent policy, someone drops in a Maps embed or the JavaScript API, and suddenly the console fills with CSP errors. The quick fix is usually script-src https://maps.googleapis.com 'unsafe-inline' plus a couple of random domains copied from Stack Overflow. That works, but it also turns a decent policy into a mushy one. ...

LaunchDarkly is one of those tools that looks harmless from a CSP perspective until it quietly breaks in production. The SDK initializes, flags never arrive, and the only clue is a blocked request buried in DevTools. I’ve seen this a lot with frontend teams that already have a decent CSP and assume feature flags are “just another script.” They usually aren’t. LaunchDarkly needs network access for streaming, polling, events, and sometimes bootstrapping behavior that doesn’t fit neatly into a locked-down policy. ...