An authenticated stored cross-site scripting (XSS) vulnerability exists in multiple WSO2 products due to improper validation of user-supplied input during API document upload in the Publisher portal. A user with publisher privileges can upload a crafted API document containing malicious JavaScript, which is later rendered in the browser when accessed by other users. A successful attack could result in redirection to malicious websites, unauthorized UI modifications, or exfiltration of browser-accessible data. However, session-related sensitive cookies are protected by the httpOnly flag, preventing session hijacking.