The XO Slider plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘get_slider’ function in all versions up to, and including, 3.8.6 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
https://plugins.trac.wordpress.org/browser/xo-liteslider/tags/3.8.6/inc/class-xo-slider.php#L315
https://plugins.trac.wordpress.org/browser/xo-liteslider/tags/3.8.6/inc/class-xo-slider.php#L247