The iWR Tooltip plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's iwrtooltip shortcode in versions up to, and including, 1.0. This is due to insufficient input sanitization and output escaping on user supplied attributes in the iwr_tooltip() shortcode handler — the title attribute is concatenated directly into an HTML attribute without esc_attr() or any other 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.