XSS in the `altField` option of the Datepicker widget in jquery-ui
### Impact
Accepting the value of the `altField` option of the Datepicker widget from untrusted sources may execute untrusted code. For example, initializing the datepicker in the following way:
```js
$( "#datepicker" ).datepicker( {
altField: "<img onerror='doEvilThing()' src='/404' />",
} );
```
will call the `doEvilThing` function.
### Patches
The issue is fixed in jQuery UI 1.13.0. Any string value passed to the `altField` option is now treated as a CSS selector.
### Workarounds
A workaround is to not accept the value of the `altField` option from untrusted sources.
### For more information
If you have any questions or comments about this advisory, search for a relevant issue in the jQuery UI repo
https://github.com/jquery/jquery-ui/issues. If you don't find an answer, open a new issue.