Oh boy a semantic argument

It turns out the language you use can be semantically ambiguous or misleading if you phrase it incorrectly. Today you learned.

And any web dev who remotely understands the point of CSP and why it was created, should instantly have alarm bells going off at the concept of triggering arbitrary ajax via html attributes.

Oh, did you finally manage to fucking Google how HTMX works so you could fish for more reasons to say it’s unsafe? What you’re describing is not a particular concern to HTMX. If an attacker can inject HTML into your page (for example, through an XSS vulnerability), they could potentially set up HTMX attributes to make requests to any endpoint, including endpoints designed to collect sensitive information. But, and this is very important, this is not a unique issue to HTMX; it’s a general security concern related to XSS vulnerabilities and improper CSP configurations.

Do you know what the correct cure for that is?

PROPER CSP CONFIGURATION.

“HTMX doesn’t bypass CSP! It just (proceeds to describe the exact mechanism by which it bypasses CSP)”

Do you genuinely not understand that CSP works on the browser API level? It doesn’t check to see if your JavaScript contains reference to disallowed endpoints and then prevents it from running. I don’t know how you “think” CSP operates, but what happens is this: The browser exposes an API to allow JavaScript to make HTTP requests - specifically XMLHttpRequest and fetch(). What CSP does is tell the browser “Hey, if you get an API request via XMLHttpRequest or fetch to a disallowed endpoint, don’t fucking issue it.” That’s it. HTMX does not magically bypass the underlying CSP mechanism, because those directives operate on a level beyond HTMX’s (or any JS library’s) influence BY DESIGN. You cannot bypass if it if’s properly configured. Two very serious questions: what part of this is confusing to you? And, have you ever tested this yourself in any capacity to even see if what you’re claiming is even true? Because I have tested it and CSP will block ANY HTMX issued request that is not allowed by CSP’s connect-src directive, assuming that’s set.

CSP works on the browser API level - all HTMX does is what you could do yourself with any AJAX: send an HTTP request to an endpoint. If the CSP disallows that endpoint, it will fail.

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Just to be clear, are you talking about some kind of templating library that literally transpiles all the htmx logic and instead packs it into individual ajax logic in js files “per element”, such that you don’t need to serve htmx client side and instead you pre-transpile all the ajax logic out to separate files?

My brother in Christ, what the fuck are you talking about “transpiling HTMX” and “serving HTMX client side?” You don’t “serve” HTMX and there’s nothing to “transpile into JavaScript.” It is JavaScript. That’s like saying you “serve React client side” and “transpile JavaScript into more JavaScript.” Jesus, I feel like I’m taking crazy pills.

Cause the very start of my statements was that if we had something like that then HTMX would be fine, as a templating lib that transpiled out to html+js.

Oh, okay, so you don’t actually know what HTMX is or how it works, then? Because HTMX (https://htmx.org/) is a JavaScript library. Like, literally just a JavaScript library. It’s like…4000 lines of JavaScript. In fact you can read the source code for it here: https://github.com/bigskysoftware/htmx/blob/master/src/htmx.js. For some…insane reason you seem to think HTMX is its own language. It’s not. It’s…just a JavaScript library. There is no other language called HTMX. There is no other mechanism or tool called HTMX. No implementation or protocol or ANYTHING else. It’s just a small JavaScript library.

invoke arbitrary logic with html attributes

Once again, HTMX enhances HTML with various attributes declaratively. It utilizes custom data attributes in HTML (like hx-get, hx-post) to specify how elements on the page should behave - essentially, how and where to fetch data or submit forms without a full page reload. This is a form of declarative programming that tells the htmx.js library (which is just doing fucking AJAX) what to do when certain events occur (e.g., a click or a form submission). The actions (like the actual requesting of data from an endpoint) are performed by the code in htmx.js.

This is a fancy way of saying “if you stick an hx-get attribute on a button, then you can just say where you want a GET request to go to and what element you want updated with the HTML returned from it and htmx.js will parse that out on page load and set an event listener for the button click to know when to initiate an AJAX request to the defined endpoint.” If you had an hx-get attribute in an element in a page and that page didn’t have the htmx.js library loaded it would do literally nothing.

And, once again, HTMX, being a JavaScript library, operates under the same security constraints as any JavaScript executed in the browser. This means that:

1. HTMX’s scripts themselves must be loaded from sources allowed by the script-src CSP directive.
2. Any dynamic requests to load content or submit data initiated by HTMX are subject to CSP’s connect-src directive.

HTMX enables arbitrary invocation of ANY api endpoint with cookies included, through html attributes, which inherently can’t be covered by Content Security Policy

I want you to please explain how HTMX bypasses the Content Security Policy connect-src directive, or any -src directive, for that matter, assuming it is specified (which it should be). Because I’m genuinely curious why the HTMX dev team would include a section on CSP in their docs if it did literally nothing, as you say.

Actually, as an even more basic question…you do know that HTMX is literally just an AJAX library, right? It doesn’t actually “do” anything via HTML attributes. The additional HTMX attributes, like hx-get, hx-post, etc. just tells HTMX where and how to make the API requests. These requests are executed by the browser’s native fetch or XMLHttpRequest APIs, depending on compatibility and implementation. Therefore, HTMX is subject to the same security constraints and policies as any other JavaScript-based operation that makes HTTP requests. Which also, by definition, means that it adheres to the Content Security Policy directives configured for that website.

In other words, an HTML button element with hx-get=“https://www.some-endpoint.com/” on it would eventually translate into

const xhr = new XMLHttpRequest();
xhr.open("GET", "https://www.some-endpoint.com/");
xhr.send();

on click.

You do understand that, right?

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