The action to remove an email from account is done using a GET request and it has security token.
The URL is :
https://www.khanacademy.org/settings/unlinkaccount?email=134hackerone%40gmail.com&fkey=<security token here>
It is never a good practice to have sensitive information in URL. Following are the reasons: + GET requests can be cached + GET requests remain in the browser history + GET requests can be bookmarked
Whereas: + POST requests are never cached + POST requests do not remain in the browser history + POST requests cannot be bookmarked
If the URL goes in the hands of malicious user then host a malicious website and perform a CSRF attack against the victim and this un-link that email address.