TeleJSON prior to 6.0.0 contains a DOM-based cross-site scripting vulnerability in the parse() function that allows attackers to execute arbitrary JavaScript by delivering a crafted JSON payload containing a malicious constructor-name property value. The custom reviver passes the constructor name directly to new Function() without sanitization when recreating object prototypes, enabling attackers to inject arbitrary JavaScript through vectors such as postMessage in cross-frame communication contexts to achieve script execution within the application.