Stencil core 4.43.5 contains a DOM-based cross-site scripting (XSS) vulnerability in the component runtime. When a downstream application enables the experimental slot fixes option and uses scoped components, assigning a string to the textContent property of such a component's host element causes the value to be parsed as HTML instead of being inserted as text. If an application writes attacker-controlled data to these host elements, the data can be interpreted as markup and script can execute in the context of the application's origin.