A stored XSS vulnerability in the Visualizer plugin 3.3.0 for WordPress allows an unauthenticated attacker to execute arbitrary JavaScript when an admin or other privileged user edits the chart via the admin dashboard. This occurs because classes/Visualizer/Gutenberg/Block.php registers wp-json/visualizer/v1/update-chart with no access control, and classes/Visualizer/Render/Page/Data.php lacks output sanitization.