You sent out a mailing from Sphere under Communications, for example. You have received reports of users who say when they clicked on the footer links, for example, Modify Your Profile, the form was prepopulated with another users information.
This typically happens if one user forwards their email to another user. For example, John forwards his email to Jane. When Jane clicks the Modify Your Profile link, John's information will be displayed as the user information associated with these footer links are John's.