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.