time to bleed by Joe Damato

technical ramblings from a wanna-be unix dinosaur

WARNING: American Express fails miserably at basic security.

View Comments

If you enjoy this article, subscribe (via RSS or e-mail) and follow me on twitter.

As of 3:35pm PST on 5/25/2010 it seems to be fixed. wireshark shows only TLS traffic now, nothing in the clear. Pretty quick fix, since this was published at 11:54am. Good deal.

This article is going to reveal a pretty serious error in a web form on the American Express Network website. I would strongly recommend NOT filling out the web form described below.

Daily Wish from the American Express Network

Daily wish from the American Express Network sent me an email this morning trying to get me to sign up for their deal of the day service where they offer a very limited quantity of products for a low price.

Sounds simple enough, right?

Well, the time of the sale is not released until the day the sale occurs, unless you are an American Express cardholder. If you are a card holder, you get a special landing page on their website telling you that if you sign up, you can get the sale times before the sale date.

The white arrow below points to the tab that only appears if you clicked through from an email from American Express. The red arrow below points to the sign up button. Take a look:

Sign up page

After clicking the sign up button (red arrow above), a lightbox appears asking for:

  • First and last name
  • American Express credit card number
  • Security code
  • Expiration date
  • Billing zip

Quite a bit of personal information, much of it sensitive. [sarcarsm]Don’t worry the page is secure[/sarcasm], see the form and the white arrow below:

The code from the form

This form looked very suspicious to me, so I decided to take a look at the code to see if the action for this sign up form was over HTTPS. Check it:

<form name="form1" method="post" action="preid2.aspx?ct=7" onsubmit="javascript:return WebForm_OnSubmit();" id="form1">

So the action is to a handler at http://dailywish.amexnetwork.com/preid2.aspx?ct=7. The lack of https doesn’t make me feel very good.

Maybe the WebForm_OnSubmit() function is doing something that might make this secure? Let’s take a look:

<script type="text/javascript"> 
function WebForm_OnSubmit() {
if (typeof(ValidatorOnSubmit) == "function" && ValidatorOnSubmit() == false) return false;
return true;

So it looks like that function is just a validator. It is really starting to feel like this form is insecure.

Let’s bring out wireshark and see what it has to say.

Wireshark packet sniff

So I filled out the form with fake information and sniffed the POST to the server.

The Daily Wish sign up form from the American Express Network is sending credit card numbers, expiration dates, and all the other personal information on the sign up form in the clear back to their server.

Holy. Fuck.


  • Do NOT fill out the form until American Express fixes this issue.

Thanks for reading and don’t forget to subscribe (via RSS or e-mail) and follow me on twitter.

Written by Joe Damato

May 25th, 2010 at 11:54 am

Posted in security

Tagged with , ,

  • Florin Andrei

    That explains the otherwise unexplainable "event" last year, when we had our AmEx card hijacked during a trip to Eastern Europe. All they needed was one attempt to login to the AmEx site.

  • Wow... that's amazing! What a screw up, somebody is getting fired...

  • skhan

    This is the cost of outsourcing...I could care less what they say!

  • given that AMEX and other credit card companies (usury companies) steal your money as fast as they can, why should they care if other people steal it too? They still make their cut when someone steals your money.

  • Brad

    Can you post the URL from the email? There is no proof anywhere in this that it loads over HTTP.

    From looking at the URL it looks like its built to load inside an IFRAME on the page.
    If the IFRAME is loaded under HTTPS there wouldn't be a problem except for if someone is in your network and forces you to load the HTTP version.

blog comments powered by Disqus