This exploit includes two vulnerabilities at Facebook:
1- An Open Redirector at the mobile domain (m.facebook.com) which is hard to detect due to its special mechanism and harder to get fixed fully because it requires an non simple change at the platform to get fully patched and it could be exploited against all Facebook users.
2- An Authentication(OAuth) Flaw that allows you to get full permissions of an application which a facebook user uses by hijacking its access_token value under a HTTP connection with the help of a MITM(Man In The Middle) attack and that allows you to get private information(like messages, emails, phones, posts and anything else) and Change his account configuration and take control of his account but that depends on the permissions of the application itself.
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#these two vulnerabilities could be exploited to work together or separately. Concerning The Open Redirector if the user clicked the redirection link while he isn't logged in to facebook a login page(form) will appear and as soon as he enters his login data he will get redirected to the url.
and concerning the authentication flaw (you need to know any application of the applications which the targeted user use to get its permissions (access_token) or we can try a popular application like skype or ask.fm app but we can't use the official apps like Facebook Messenger..)>
#Can't explain more about them otherwise they would be public!