CVE-2026-16090: GamiPress <= 7.9.9.1 - Authenticated (Contributor+) Stored Cross-Site Scripting via gamipress_achievement Shortcode

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 'gamipressachievement' 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. WordPress save-time wpksespost does not neutralize this payload because the injected value is stored inside a shortcode attribute rather than as a raw HTML tag, and is only emitted into HTML at render time without escaping.