WPBakery Page Builder <= 8.6.1 - Stored Cross-Site Scripting via vc_custom_heading Shortcode

The WPBakery Page Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the vc_custom_heading shortcode in all versions up to, and including, 8.6.1. This is due to insufficient restriction of allowed HTML tags and improper sanitization of user-supplied attributes in the font_container parameter. This makes it possible for authenticated attackers with contributor-level access or higher to inject arbitrary web scripts in posts that will execute whenever a user accesses an injected page via the vc_custom_heading shortcode with malicious tag and text attributes granted they have access to use WPBakery shortcodes.