Three Information Disclosure Vulnerability

A few weeks ago, I got an email from Three asking me to fill out a survey for them, rating my satisfaction with their services. They offered “the chance to win an iPad”, so I decided I’d fill in the survey to provide some feedback (I’m generally a fairly satisfied customer).

The link opened in my default web browser (Firefox), which happened to be linked up to Burp – after filling and submitting the survey, I was able to view the requests and responses that Firefox had made during the process. After looking at these requests, I noticed something quite worrying.

The site (https://www.threemicrosites.co.uk/survey/, now closed) was making an AJAX request to an API (http://www.threemicrosites.co.uk/api/getuser/p/44xxxxxxxxxx/, where xxxxxxxxxx is the 3 phone number). The request was made over cleartext HTTP, passing my mobile phone number in the URL. The response included my 3 account number, my full name, my email address and some other account identifier. I confirmed that this was the case for other numbers by entering a friends phone number (with their permission) – sure enough, their name and contact details were presented to me.  Information from the API was presented in the following form, as JSON:

{"success":true,"id":"813xxx","user_id":"9555xxxxxx","phone":"447598xxxxxx","email":"xxxxxx@yyyyy.zzz","title":"Mr","name":"Joseph","surname":"Redfern","email_vs_sms":"xxx","timestamp":"2015-05-xx xx:xx:xx"}

Clearly, this information disclosure isn’t ideal. The ability to find out the account holder and contact details behind ANY 3 phone number could come in handy for social engineering attacks, stalking, spamming etc. It would also be possible to scrape the API and build up a database of 3 customers by brute-forcing the API using H3G Number Prefixes, which can be found here – such a database could be very valuable to Three’s competitors,  marketing companies etc. I’d consider it a fairly severe breach of privacy.

The bizarre thing is that the survey didn’t appear to use any of the information returned by the API – the thank you page had no reference of my name, email address or account number.

I reported the issue to Three customer support, and requested that I be notified once their security team had acknowledged the issue. Customer Support said that they’d pass the request on, but that they couldn’t promise anything – sadly, they didn’t bother to get back to me (and I didn’t even win their competition!). The survey has now been taken down, along with the offending API. I can’t be sure if this was in response to these issues, or if the closure was planned – but either way, this no longer seems to be a problem.

Video Demo:

7 thoughts on “Three Information Disclosure Vulnerability

  1. Its very sad to see this site go to sleep, it was my salvation a while back when I was out of work, depressed and in serious need of fnm shaped distraction. Cant thank you enough for all your hard work and enthusiasm, its been great. Heres hoping for some major fnm news / developments to wake 2.0 from its slumber! In the meantime Adrian, all the best with fatherhood and life in general, and hope to bump into the rest of you guys somewhere else on the web.

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