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А эти пароли сохранены в Internet Explorer, или же могут в любом браузере (но чтобы отображались именно в этом диспетчере учётных данных)? »

Там же по ссылке написано:

Windows Credentials Certificate-Based credentials Generic Credentials

Плюс на новых версиях, начиная с 8.1, еще добавились Web Credentials:

Represent logon information for websites that is stored by Windows, Skype, Internet Explorer or other Microsoft apps.

Generic Credentials:

Generic credentials are defined and authenticated by applications that manage authorization and security directly instead of delegating these tasks to the operating system. For example, an application can require users to enter a user name and password provided by the application or to produce a certificate to access a website. Applications use Credentials Management functions to prompt users for application-defined, generic, credential information, such as user name, certificate, smart card, or password. The information entered by the user is returned to the application for authentication. Credentials Management provides customizable cache management and long-term storage for generic credentials. Generic credentials can be read and written by user processes.

Вывод: да, это могут быть и сторонние приложения.