I recently accessed iCloud Website using a device that I don't personally own and generally use.
After successfully logging-in by entering my Apple ID/Password and the Two Factor Authentication code, I was asked if I would like to trust the browser, so as to skip entering Two Factor Authentication code every time I login, I complied. (It isn't a public device and there is no possibility of unauthorized access)
This gave me the of flexibility to easily login in with just my Apple ID and password when I don't have any of my trusted Apple device around to get the Two Factor Authentication code.
Now, I am done using the device and will be returning it to the original owner. How do I untrust the Web browser?, i.e. require it to ask for Two Factor Authentication code next time a login is performed using my Apple ID? Also, is there a way to see a list of all similar trusted browsers and untrust them?