In Progress® Kendo® UI for jQuery prior to 2026.3.1015, the Splitter and Window components starting with version 2011.2.804 and the Tooltip component starting with version 2013.1.319 construct iframe markup without properly sanitizing URL values or encoding the Window iframe title. An attacker with low privileges who can control these values can inject HTML attributes, including JavaScript event handlers, through an apostrophe in an iframe URL or a crafted title. When a user interacts with the affected component, injected JavaScript can execute in the user's browser context, compromising the confidentiality and integrity of accessible data.