Sometime back, I noticed a strange problem with Facebook, I had
accidentally entered wrong password in Facebook, and it showed my first and
last name with profile picture, along with the password incorrect message. I
thought that the fact that it was showing the name had something to do with
cookies stored, so I tried other email id's, and it was the same. I wondered
over the possibilities, and wrote a POC tool to test it.
This script extracts the First and Last Name (provided by the users when
they sign up for Facebook). Facebook is kind enough to return the name even
if the supplied email/password combination is wrong. Further more,it also
gives out the profile picture (this script does not harvest it, but its easy
to add that too). Facebook users have no control over this, as this works
even when you have set all privacy settings properly. Harvesting this data
is very easy, as it can be easily bypassed by using a bunch of proxies.
As Facebook is so popular, some implications -
1) Someone has a list of email address that he has no clue about. He can
feed them to Facebook one by one (or in a list, using a script like this)
and chances are that he'll get more than 50% hits. Useful for phishing
attacks (People will get more convinced when they see their *real* names).
2) One can generate random email addresses, and *verify* their existence .
Hint: You can generate emails using (common names + a corporate domain), and
check them against Facebook. Might come handy in a Pentest.
Rest is only left up to one's imagination.
Find the POC script attached.
PS: I did not report this, as I am unsure on what to call it, a "bug",
"vuln" or a "feature".
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