The Webform module, used for creating forms and processing submissions, contains a flaw in how it handles Remote Post handlers. These handlers send data to external servers via APIs. The module fails to sufficiently filter response values from the Remote Post handler before they are rendered through handler response tokens. Consequently, if a site uses these tokens in rendered output, a remote endpoint could return values that are rendered as HTML, leading to cross-site scripting (XSS), where malicious scripts are injected into trusted websites. Approximately 436,300 instances were identified globally.