Clust is adding another layer of protection to document collection by adding a password on their portal.
To ensure the highest level of protection possible, the password added by recipients isn’t stored or tracked by us in any way, that's the reason why they cannot recover their password once lost. (You'll have to send a new request)
They can protect the portal access with a password but it's their responsibility to remember and share the password with any other recipient(s).
From your dashboard you can also invite contributors to any request so they can also jump in and share their feedbacks from a dedicated collaborative portal.
It's also your responsibility (whether you use Clust or not) to make sure only allowed contributors see your recipient documents and information.