Extra Settings for RocketChat <= 0.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via Shortcode Attributes

The Extra Settings for RocketChat plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'rocketchat' shortcode's 'title' attribute in versions up to, and including, 0.1. This is due to insufficient input sanitization and output escaping in the rxstg_shortcode() function, which concatenates the user-supplied 'title' attribute directly into HTML output. 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.