An issue exists in the Express view engine wrapper for Handlebars where the Node.js process can crash during output escaping. This occurs when an async helper, registered via `registerAsyncHelper()`, resolves to an object with a `toHTML` property that is truthy but not callable. The `escapeExpression()` function attempts to call `toHTML` as a method, resulting in a TypeError. Because the async substitution executes on a later tick outside the render function's try/catch block, the error becomes an uncaught exception that terminates the process without sending a response. This can be triggered remotely if an async helper resolves to an externally influenced object, such as parsed JSON.