The plugin does not sanitize and escape some of its default slideshow settings, which could allow high-privileged users such as admin to perform Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed
As admin, put the following payload in the "Number of seconds the slide takes to slide in", "Seconds between changing slides" or "Seconds between changing slides" general settings of the plugin (/wp-admin/edit.php?post_type=slideshow&page=general_settings): <script>alert('XSS');</script>
The XSS will be triggered when creating a new Slideshow (/wp-admin/post-new.php?post_type=slideshow), as well when editing any slideshow