Which of the following statements about cookies is true?

Cookies are small pieces of data that websites store on a user's device to remember information about the user between sessions. The statement that cookies are left behind by visited websites is accurate because whenever you visit a website, the website can create a cookie and save it on your device. This cookie can include various information, such as user preferences, login credentials, and tracking information, which helps enhance the user experience during future visits.

The other statements do not reflect how cookies function accurately. For instance, cookies do not contain executable code; they are strictly data strings. Additionally, cookies can indeed be harvested by third parties if they have access to the user's browser or if the cookies are not properly secured. Lastly, cookies do not provide real-time updates on browsing history; they merely store information that the website can retrieve later, rather than actively tracking browsing activities as they happen.