Reusable Text Blocks <= 1.5.3 - Authenticated (Author+) Stored Cross-Site Scripting via Shortcode

The Reusable Text Blocks plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'text-blocks' shortcode in versions up to, and including, 1.5.3 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with author-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.