Ways to prevent the execution of JavaScript code?

I have a website that contains a block where AJAX-loaded code is coming from a remote server. How can I prevent potentially harmful code from executing, especially when it originates from a remote source? Is using the "noscript" tag sufficient to protect against this risk?

I believe it's important not to overlook scenarios in which code like

</noscript><script>...</script>
may be present.

Thank you for your help!

Answer №1

What steps can be taken to prevent the execution of potentially harmful code from a remote server?

To protect against executing malicious code from a remote server, make Ajax requests to your own server instead. Retrieve data from the remote server through your server, and then pass it through an HTML parser and a whitelist (XSS filter) before sending it back to the client.

Is using the "noscript" tag sufficient for security reasons?

The noscript tag is designed to provide content that browsers will ignore if JavaScript is disabled. However, it does not offer any protection or sandboxing capabilities against malicious code.

Answer №2

If you want to load a specific element via ajax, you can target it using a selector. Here's an example to clarify:

http://jsbin.com/efazun/2 - (Page 1) Contains an alert that says 'hello world' when the page loads.

http://jsbin.com/ezewep/4/edit (Page 2) - uses jQuery load to load Page 1, which displays the hello world message (this executes the script on load - not ideal).

http://jsbin.com/ezewep/2/edit (Page 3) - uses jQuery load to load Page 1, but only targets the text without executing any scripts (so no hello world message shows up).

For more information: http://api.jquery.com/load/

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