SKT Skill Bar <= 2.6 - Authenticated (Contributor+) Stored Cross-Site Scripting

The SKT Skill Bar plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the `chart_size` attribute of the `skillwrapper` shortcode in all versions up to, and including, 2.6. This is due to insufficient input sanitization and output escaping on the `chart_size` attribute, which is concatenated directly into an inline `<style>` block. 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.