CWE-1004: Sensitive Cookie Without 'HttpOnly' Flag

The HttpOnly flag directs compatible browsers to prevent client-side script from accessing cookies. Including the HttpOnly flag in the Set-Cookie HTTP response header helps mitigate the risk associated with Cross-Site Scripting (XSS) where an attacker's script code might attempt to read the contents of a cookie and exfiltrate information obtained. When set, browsers that support the flag will not reveal the contents of the cookie to a third party via client-side script executed via XSS.

An HTTP cookie is a small piece of data attributed to a specific website and stored on the user's computer by the user's web browser. This data can be leveraged for a variety of purposes including saving information entered into form fields, recording user activity, and for authentication purposes. Cookies used to save or record information generated by the user are accessed and modified by script code embedded in a web page. While cookies used for authentication are created by the website's server and sent to the user to be attached to future requests. These authentication cookies are often not meant to be accessed by the web page sent to the user, and are instead just supposed to be attached to future requests to verify authentication details.