The xmlhttprequest-ssl package before 1.6.1 for Node.js disables SSL certificate validation by default, because rejectUnauthorized (when the property exists but is undefined) is considered to be false within the https.request function of Node.js. In other words, no certificate is ever rejected.

This affects the package xmlhttprequest before 1.7.0; all versions of package xmlhttprequest-ssl. Provided requests are sent synchronously (async=False on xhr.open), malicious user input flowing into xhr.send could result in arbitrary code being injected and run.