Neatly Bypassing Content Security Policy (opens in new tab)

I think a few reasons:

1. It's not a sufficient replacement for sanitizing input. You need to sanitize; CSP is just an extra layer of protection.

2. relative new.

3. many popular frameworks don't support it out of the box.

It's especially annoying on github.

That said, that report also notes that there is growth. A site I manage, https://bestpractices.coreinfrastructure.org , does use CSP in practically every page. There's one page where we had to weaken the CSP requirements, but that page doesn't include any data directly created by a user (so the risk is not low). The most recent version of CSP has some features that may make transition easier (once sites believe they can depend on it). There's reason to hope that CSP will become more common, but it's going to take time.

The spec revisions are a little arduous, but in my experience the biggest problem is that any site big enough to start caring about CSP is also big enough to have a myriad of trackers and JS snippets that insist on using these unsafe features. Google Tag Manager might as well have been based on weaponized XSS payloads.

And now the technical problem is actually a human problem because some poor security schmuck has to convince a totally different team with a totally different reporting structure (those trackers likely go up into sales or marketing, possibly some random SEO contractor you've barely heard of!) to prioritize a pretty fundamental change.

Maybe the security person tries to walk up their reporting chain until the two converge, possibly at the CEO. But it sure sounds like you're trying to kill a feature for intangible goals (it may or may not prevent an XSS vuln, you say?). And the team that owns the feature will tell you they can directly attribute growth to the visibility they get from that feature.

Even when it isn't SEO's fault, a lot of sites legitimately use inline scripts in order to shovel some server-side JSON into the rendered HTML quickly where eventually some JS can access it for example. You can use DOM elements with data attributes, but that's probably not how it works today because that's not the obvious way to do it.

There's also ' frame-src' for content security policies, which lets you control what is allowed in the iframe's src. Even with these guards in place, you generally should not let user content drive an iframe's src

[0] https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Co...