The Skype Legacy Buttons plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'skype-status' shortcode in all versions up to, and including, 3.1 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with contributor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
https://plugins.trac.wordpress.org/browser/skype-online-status/tags/3.1/skype-classes.php#L316