GHSA-c78w-2gw7-gjv3

### Impact
A cross-site scripting (XSS) vulnerability was discovered in: the core parser and `media` plugin. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor via the clipboard or APIs. This impacts all users who are using TinyMCE 4.9.9 or lower and TinyMCE 5.2.1 or lower.

### Patches
This vulnerability has been patched in TinyMCE 4.9.10 and 5.2.2 by improved HTML parsing and sanitization logic.

### Workarounds
The workarounds available are:
- disable the media plugin and manually sanitize CDATA content (see below)
or
- upgrade to either TinyMCE 4.9.10 or TinyMCE 5.2.2

#### Example: Manually strip CDATA elements
```js
setup: function(editor) {
editor.on('PreInit', function() {
editor.parser.addNodeFilter('#cdata', function(nodes) {
for (var i = 0; i < nodes.length; i++) {
nodes[i].remove();
}
});
});
}
```

### Acknowledgements
Tiny Technologies would like to thank Michał Bentkowski and [intivesec](https://github.com/intivesec) for discovering these vulnerabilities.

### References
https://www.tiny.cloud/docs/release-notes/release-notes522/#securityfixes

### For more information
If you have any questions or comments about this advisory:
* Open an issue in the [TinyMCE repo](https://github.com/tinymce/tinymce/issues)
* Email us at [[email protected]](mailto:[email protected])