HAX CMS helps manage microsite universe with PHP or NodeJs backends. Versions up to and including 26.0.0 are affected by a stored cross-site scripting (XSS) vulnerability in the `/system/api/saveNode` endpoint. An authenticated user with a permission to edit pages can bypass the HTML sanitizer by injecting an event handler attribute without whitespace before the attribute name. @haxtheweb/haxcms-nodejs 26.0.1 and haxcms-php 26.0.2 patch the issue.

Affected: npm: @haxtheweb/haxcms-nodejs

## Summary

HaxCMS is affected by a stored cross-site scripting (XSS) vulnerability in the `/system/api/saveNode` endpoint. An authenticated user with a permission to edit pages can bypass the HTML sanitizer by injecting an event handler attribute without whitespace before the attribute name.

For example, the sanitizer misses:

```html <a href="#"onclick="alert('kn1ph')">click me</a> ```

The important bypass is:

```html href="#"onclick= ```

The payload is stored in the generated page files and executes when a user clicks the injected link.

## Details

The issue is caused by regex-based HTML sanitization that expects whitespace before event handler attributes. Because the sanitizer expects a pattern like:

```html href="#" onclick="..." ```

It fails to remove an event handler when it is written without whitespace:

```html href="#"onclick="..." ```

Browsers still parse `onclick` as a valid event handler attribute, so the JavaScript executes when the element is clicked.

Affected endpoint:

```text POST /system/api/saveNode?site_token=[VALID_SITE_TOKEN] ```

Affected parameter:

```text node.body ```

## PoC

1. Log in to HaxCMS and edit any existing page.

2. Capture the page save request in Burp Suite:

```text POST /system/api/saveNode?site_token=[VALID_SITE_TOKEN] ``` 3. In the JSON request body, modify only the `node.body` value.

Change: ```json "body":"...existing page content...\n" ``` To: ```json "body":"...existing page content...\n<a href=\"#\"onclick=\"alert…