CVE-2026-15730: GamiPress <= 7.9.9.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'heading_size' Shortcode Attribute

The GamiPress – Gamification plugin to reward points, achievements, badges & ranks in WordPress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'headingsize' Shortcode Attribute in all versions up to, and including, 7.9.9.1 due to insufficient input sanitization and output escaping. 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. The wpksespost filter applied at post save does not neutralize this payload because only the inert shortcode text is stored in postcontent; the dangerous HTML is synthesized at render time by the shortcode handler, entirely bypassing save-time sanitization.