Certitude is a client of the geocaching live API (Application Programming Interface) to provide a seamless integration of certitude with geocaching.com. This is as close as it gets to having a coordinate verifier on the cache page itself. Here is how it works.
On some certitude pages, you will see an invitation to sign in to identify yourself. When you click on the link, you should be directed to the geocaching.com site sign-in page:
Note that if you're already signed in, you would be directed to the page described below. Please note that while you enter your credentials, you are on the geocaching.com site and certitude has no visibility of your username or password.
You will then be directed to this page:
What this message means is that you are authorizing certitude to access some information on your behalf on the geocaching.com site. What 3rd party applications like certitude can access is some public information any user with an account can already see on the site: cache pages, trackables, user profiles, etc... Some private information they can also access are the user's home coordinates, cache notes, or pocket queries. None of the user's private information like real name, address, phone number or private pictures are accessible. Certitude only uses your geocaching name for display purpose and the ability to update your cache note when you solve a puzzle.
If you choose to not allow certitude to access geocaching.com on your behalf, you will still be able to use certitude anonymously to verify puzzle solutions. Note however that you will be very limited in the number of attempts you can make on a given puzzle in order to restrict brute forcing efforts. Also, you won't be able to update your cache page note or create a puzzle solution. If you decided to change your mind later, you can always come back to this page.
If you choose to grant certitude access to geocaching.com, you will be brought back to the certitude page you came from with your geocaching name appearing on the left side. You will also receive a confirmation email from geocaching.com. You won't have to go through this process again, unless you switch to a different browser or device. You will still be able to solve puzzles anonymously if you wish, while still having the ability to update the cache page note with the final solution and certitude bonus info.