Gerrit Luimstra Gerrit Luimstra - 1 year ago 196
HTML Question

How to sandbox a div element?

I am trying to build a content editor. This contenteditor will load a HTML document (with JavaScript) into for example a #result element. The problem with this, is that if inside this HTML element there is for example

, then all of my inputs are gone throughout the whole page, so not just inside the loaded HTML (my goal).

What I want to do with the editor is when a client clicks on an element that represents something in the database, the info of this element will popup and the user will be able to edit this. (So, if a user hovers over a form with the class "contact-form" (which is in the database, connected to the loaded page) a new window will popup with information about this specific form element.

Also, I cannot completely disable Javascript, since the loaded HTML might contain Javascript for styling etc.

My goal: Remove Javascript, that can be annoying when a user loads in an HTML file. Like an alert(); Also, remove the ability for the Javascript to edit somehthing outside it's own DOM.

P.S. I am open to better workarounds like using an iframe for this, BUT I want to be able to hover over elements in interact with them.

Edit: It seems that this question might be a bit too broad, looking at the comments. Summary of my question: How can I disable alert() for a specific div and how can I create a sandbox so that code inside a div, can only change elements from inside that div.

Answer Source

What you're looking for is HTML sanitization. This is the process by which you remove any dangerous content from a snippet of HTML on the server, before it's loaded in the browser. There are plenty of sanitization libraries out there that can strip script tags, object tags, etc. Just remember, you can't sanitize using javascript because by the time you've injected your script, another malicious script may have already loaded and run.

The only way to effectively sandbox a javascript environment is with iframes. You'll notice that websites like CodePen, JSBin and JSFiddle use them extensively. There's something called the ShadowDOM, which is the basis of Web Components, but it isn't very well supported yet.

To make it possible to run your own frontend scripts that allow for hovering, you can inject your script after your sanitization process. This way, if it's loaded inside an iframe your script will also be loaded.

Finally, alert() doesn't belong to any elements on the DOM. You can trigger an alert as soon as the page loads, for example. However, if you're trying to prevent alerts from popping up on user interactions, you could try removing all event listeners from a particular element. This won't be necessary if you sanitize the HTML of script tags, however, since the script wouldn't have had a chance to load so there won't be any event listeners.

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