Social workspace login validation URL redirects to an error message

For the moment, the validation URL sent by email is wrong, but one can edit it to remove the wrong part.
Once the URL is manually corrected (e.g. https://intranet.nuxeo.com/nuxeo/site/userRegistration/validate/f3583cac-64db-4486-b668-27caec4f2e06) and pasted in the browser, I reach a page saying: "You don't have the necessary permission to do the requested action". The URL seams to be the document URL, e.g. https://intranet.nuxeo.com/nuxeo/nxpath/default/collaboration/Component%20Model@view_documents
If I sign out/sign in, I can access the social workspace.

see also NXP-10072