The WP Circliful plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'id' shortcode attribute of the [circliful] shortcode and via multiple shortcode attributes of the [circliful_direct] shortcode in all versions up to and including 1.2. This is due to insufficient input sanitization and output escaping on user-supplied shortcode attributes. Specifically, in the circliful_shortcode() function, the 'id' attribute value is concatenated directly into an HTML id attribute (line 285) without any escaping, allowing an attacker to break out of the double-quoted attribute and inject arbitrary HTML event handlers. Similarly, the circliful_direct_shortcode() function (line 257) outputs all shortcode attributes directly into HTML data-* attributes without 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.