Thursday, September 27, 2012

Analysis of Dom Xss vulnerability in a Facebook Like Button implementation

Note: The following vulnerability is now patched. Thanks to Matt, Charlie and to the team that released a patch yesterday after receiving our advisory.


I like very much facebook, and I like clicking on facebook like buttons like the one below. has its own implementation of Facebook Like Button and is very used among internet websites. They estimate that unique websites around the world are several millions.

A Facebook Like Button in a Share Widget Bar:

You can find some background information already in one of our previous posts:


Proof of Concept"></fb:like><img/src="aaa"/onerror="alert('DomXss Found!')

Note: This reflected dombased cross site scripting (before the patch) was present in a tremendous number of websites

Vulnerable Code

if (F.href === _1) {
d = _8.util.clone(E.share.url_transforms || {});
d.defrag = 1;
F.href = _8.track.mgu(E.share.url, d);//-- Location
for (A in F) {
B += " " + A + "=\"" + F[A] + "\"";//-- Attribute Set
if (!E.share.xid) {
E.share.xid = _8.util.cuid();
f[F.href] = {};
for (A in E.share) {
f[F.href][A] = E.share[A];&nbsp; 
G.innerHTML = "<fb:like br="br" 
ref="\">_8.share.gcp(E.share, E.conf,".like").replace(",", "_") 
+ "\" " + B + "</fb:like>"; //-- DomXss

Analysis and discovery with DOMinatorPro

Even if to the reader this issue seems like a common cross site scripting, finding such kind of security issues in Javascript code (aka DomXss) is an extremely complex task.

This is why our Advanced Research team developed DOMinatorPro. DOMinatorPro can be downloaded from the following dedicated website:

DOMinatorPro is a Free Opensource Project with Commercial Extensions. Commercial extensions have a 15 days Free Trial Period.

The vulnerability was in ONE of the scripts loaded by the “addthis_widget.js”  script available online at “”. As you can see multiple scripts are loaded and the scripts are compressed and obfuscated , giving to human security reviewers a painful and a very long and time comsuming task to accomplish.

Note: The following part is taken from the DOMinatorPro user manual and shows a similar vulnerability in a demo context. In DOMinatorPro user manual you can find sample cases to help you understand the cause of the vulnerability for producing solid Javascript patches.

By the way, when browsing to a website with a vulnerable “Facebook - Like Button” with DOMinatorPro tool you will see in a couple of seconds the following alert:

From the previous screenshot the very interesting information is that you got an HTML Injection (e.g. Cross Site Scripting) from the location.href (e.g. the URL).
Important Note: Sink describes where the vulnerability is and the Source is where the controllable input comes from.

Summary of the issue: HTML injection vulnerability coming from a user supplied input location.href (URL)

 Source History

Next step is to check where this issue has been found. This is easy, looking at the source history:
Exact location of the issue is: 
  • http://www.vulnerablewebsite.con/webpage.aspx?menuid=3#injectedstring<>”’

Source history is a simplified call stack that shows the content of controllable strings.
Location.href can be controlled and the value is showed up in light green, after this string is concatenated with another string by left and by right.
As it is possible to see from the above picture, it’s also possible to check if there are validator functions in place by injecting HTML patterns after the # (hash); in this case I injected the pattern #injectedstring<>”’ after the vulnerable URL. Using the “Hash” sign is important because anything coming after it will not be sent to the server.
It’s possible to see from the last line that #injectedstring<>"' is not encoded (typical encoded string is in the form of: #injectedstring%3c%22%27).
By supplying now the correct exploit it is possible to turn the vulnerability into a reflected DOM cross site scripting attack:

Standard HTML Injection Payload: 
  • <img/src="aaa"/onerror="alert('DomXss Found!')">
Important Note: Thanks to DOMinatorPro Browser emulation feature we can mimic different browser insecure behaviors. This permits to show developers the vulnerability inside DOMinatorPro/Firefox, even if the previous exploit works only under Internet Explorer.

Call Stack 

Now for a developer it is time to open the “Call Stack”:

The Call Stack interactively shows where the vulnerability is with the correct line. It is possible to see “document.location.href” is not escaped properly.
It’s very important to output encode the value before it is displayed.


Correct fixing at line 116:
•    Use the “encodeURIComponent()” function.

Tuesday, September 25, 2012

Temporary Patch for a Dom Xss 0day in Widgets

Note: fixed this issue yesterday 26/09/12 thanks to team for fixing it so rapidly!

Including a Javascript code in your homepage from another Website is a very common practice.

"Third party scripts are a hidden-potential security threat" for example provides very useful scripts to help enhancing a website with the most used social media networks. From Wikipedia: “ AddThis is a widely used social bookmarking service that can be integrated into a website with the use of a web widget. Once it is added, visitors to the website can bookmark an item using a variety of services, such as Facebook, MySpace, Google Bookmarks, Pinterest, and Twitter.[2]”.

AddThis social plugins and analytics are used by "over 14 million sites worldwide” (2007).

You just need to “add this”:

There are many advantages in doing this:
•    code will be updated by the maintainer
•    bugs will be fixed silently
•    … many others

Unfortunately it also hides several drawbacks:

•    Security vulnerabilities in referenced scripts will affect your website

During the past year we analyzed many Javascript codes belonging to tracking cookies. Some of those analysis have been pretty interesting. During 2011 we reported for example several issues in Omniture Catalyst Javascript code, with documented proof of concept code (

The DomXss Vulnerability

DOM-based Cross-Site Scripting is the de-facto name for XSS bugs which are the result of active browser-side content on a page, typically JavaScript, obtaining user input and then doing something unsafe with it which leads to execution of injected code. This document only discusses JavaScript bugs which lead to XSS.

More information about DomXss vulnerabilities can be found here:

DomXss in Widgets

Details of the vulnerability have been temporarily omitted because the number of affected websites is huge. We did this for giving enough time to the vendor for fixing the issues (full details have been sent to

Note from 26/09: Investigating further, it seems that vulnerability is not always triggered; this may depends from the templates used
Note from 27/09: Details about the issue can be found here

Vulnerability has been found using DominatorPro, our DomXss Analyzer. Dominator is an opensource project with several extensions (some of these are commercial) and can be downloaded for free at

A temporary patch

You can make this temporary patch by configuration for protecting your website in the meantime that the vulnerable code will be fixed. Note: this patch is not for the vulnerability itself but will prevent it from being easily exploited.

To patch a vulnerable Widget manually populate the following property:

•    addthis:url

For more information visit:



<div addthis:url="" class="addthis_toolbox addthis_default_style" nbsp="nbsp"> 

If you don’t add this, you are potentially vulnerable. 

ZeuS Gameover Overview

In this blog post we are going to discuss about an interesting ZeuS variant called “Gameover” that in the last quarter shown an impressive activity in terms of spread and infection rate especially in Italy.
According to f-secure [1]:

 “Italy has a significant number of Gameover infections.”

And according to the Secureworks [2]:

“on 678,000 unique Gameover bots, of which, 5.1% are Italian.”

ZeuS Gameover is a post source-code-leak variant of the original ZeuS trojan. One of the most peculiar characteristics of Gameover is that it relies upon a Peer to Peer botnet infrastructure, in such way that removes the centralized Command and Control server ([2]), additionally it implements a DGA (Domain Generation Algorithm) which produces domains like these in case the peers cannot be reached:


According to Symantec [3]:  “every peer in the botnet can act as a C&C server, while none of them really are one. Bots are now capable of downloading commands, configuration files, and executables from other bots—every compromised computer is capable of providing data to the other bots. We don’t yet know how the stolen data is communicated back to the attackers, but it’s possible that such data is routed through the peers until it reaches a drop zone controlled by the attackers.”

Gameover WebInjects

Like other ZeuS versions, Gameover bases its attacks on the MiTB (Man in The Browser) approach; this implies that the malware has a configuration file which contains a list of financial institutions and the relative malicious JavaScript code to be injected when a victim visits one of these pages.
An interesting aspect of this variant, is that configuration and the whole Web Injection mechanism is significantly different from previous ZeuS versions.
WebInjection/Configuration management is demanded to a malicious thread injected into the running browser process (like other versions) and can be synthetized as follows:

•    Configuration Decryption
•    Regular Expressions interpretation in order to find matching URLs
•    Web Injection code decryption and commit into the victim page

The malicious thread will take the URL infected by the victim in order to match this with an encoded list of URLs, which constitutes the Target Institutions.
Here comes one of the peculiar characteristics of Gameover, which is given by the fact that there is a double list of target URLs:

1.    List of “Default” targets
2.    List of Web Injection targets

Basically URL matching goes through two lists of targets, the first one which is already public and known:
•    @
•    @*
•    @*
•    @*
•    @*
•    @https://**
•    @*
•    @*
•    @https://**

This partial list (the complete one contains targets from various countries) shows the targeted Italian financial institutions [1]

The analysis of multiple samples and configurations showed that this list is near to be immutable, especially about Italian targets.

But by going a little deeper into the configuration decryption process, Minded Security observed that there is a second list of targets, significantly larger than the first, which contains a huge amount of financial institutions targeted by the web injection. Below the complete list of Gameover targets:

Full list can be downloaded from:

According to the Reverse Engineered code, this second list comes from the same configuration used for the first and it’s decrypted immediately after that the default one has been checked.
Due to the same logic behind the decryption process, it’s possible to catch this list in the same way used to carve the default one, like in the screenshot below:

An aspect to note is that, the URL triggers are not immediately visible this time, because of the following pattern adopted:
True_Char – 0x1C – True_Char – 0x1C – etc.
True_Char – 0x1D – True_Char – 0x1D – etc.
When victim’s URL matches with one of the above, the corresponding web inject will be decrypted and injected into the target page.

Gameover ATS
Let’s now take a closer look to a typical Gameover injected malicious JavaScript code:

_GATE = 'https://dom*.eu/*/php/gate.php?d=';
window.pseudo = [];

As you can see _GATE contains an external resource (obscured for security reasons), this location will be used to gather all stolen information.

This technology is known as ATS (Automated Transfer System) [4]:

Unlike WebInject files that displayed pop-ups to steal victims’ credentials, ATSs remained invisible. These did not prompt the display of pop-ups as well as performed several tasks such as checking account balances and conducting wire transfers using the victims’ credentials without alerting them. ATS scripts also modified account balances and hid illegitimate transactions to hide traces of their presence to victims. As long as a system remains infected with an ATS, its user will not be able to see the illegitimate transactions made from his/her accounts. This essentially brings to the fore automated online banking fraud because cybercriminals no longer need user intervention to obtain money.

In other words an ATS system allows criminals to manage stolen information simply by accessing a web application, the following screenshot show the login page of a typical ATS application.

Following there is a screenshot taken from one of those ATS domains that shows the Automated Transfer Rule building:

And here there is another screenshot from the same ATS which targets a different bank:

It’s finally pretty interesting to put in evidence the fact that the usage of an ATS web inject changed the way dropzones work, because they will be no longer a centralized resource (easy to monitor and consequently takedown),  but a distributed one.
Each webinject could contain a different ATS server.   

Trackdown ATS users

As final step Minded Security decided to track down the ATS system in order to observe the involved user activity, shown below a Geo Map of the observed access. Users' logged IP come out from cloud server, in this way they can protect their identity.


Gameover poses a serious risk not only for Italian financial institutions; Minded Security will maintain a high awareness level on the evolution of this threat.



Tuesday, September 18, 2012

BSIMM4 Release Expands Software Security Measurement Tool and Describes New Activities

The BSIMM project continues to expand with data from 51 leading firms in 12 vertical markets and is now ten times its original 2009 size.

BSIMM4 encompasses ten times the measurement data of the original 2009 study (95 distinct measurements), and reports on two new activities, bringing the activity count going forward to 111.

The BSIMM4 project provides insight into fifty-one of the most successful software security initiatives in the world and describes how these initiatives evolve, change, and improve over time. The multi-year study is based on in-depth measurement of leading enterprises including Adobe, Aon, Bank of America, Box, Capital One, The Depository Trust & Clearing Corporation (DTCC), EMC, F-Secure, Fannie Mae, Fidelity, Google, Intel, Intuit, JPMorgan Chase & Co., Mashery, McKesson, Microsoft, Nokia, Nokia Siemens Networks, QUALCOMM, Rackspace, Salesforce, Sallie Mae, SAP, Scripps Networks, Sony Mobile, Standard Life, SWIFT, Symantec, Telecom Italia, Thomson Reuters, Vanguard, Visa, VMware, Wells Fargo, and Zynga.

Originally launched in March 2009, the BSIMM is the industry's first software security measurement tool built from real-world data rather than based on philosophy and theory. BSIMM2 was released in May 2010 and tripled the size of the original study from nine organizations to thirty. BSIMM3 was released in September 2011 with data from forty-two firms and included a longitudinal study showing how software security initiatives have grown over time. BSIMM4, released today, covers fifty-one firms representing a range of twelve overlapping verticals including: financial services (19), independent software vendors (19), technology firms (13), cloud (13), media (4), security (3), telecommunications (3), insurance (2), energy (2), retail (2) and healthcare (1). The current release includes updated activity descriptions, two new activities and a longitudinal study.

“The BSIMM work is exciting not only because of its data-driven scientific approach to measurement, but also because of the community we have established,” said Dr. Gary McGraw, Cigital’s CTO. “There is nothing more satisfying than enabling top software security initiatives worldwide to cooperate in moving software security forward.”

Using the BSIMM measuring stick, Dr. Gary McGraw, Sammy Migues, and Jacob West conducted a series of in-person interviews with executives in charge of the fifty-one software security initiatives to collect data for BSIMM4. For the first time in the BSIMM project, new activities were observed in addition to the original 109, resulting in the addition of two new activities to the model going forward. The activities are: Simulate software crisis and Automate malicious code detection.

Some numerical highlights of BSIMM4:

- BSIMM4 includes 51 firms from 12 industry verticals
- BSIMM4 has grown 20% since BSIMM3 and is ten times bigger than the original 2009 edition
- The BSIMM4 data set has 95 distinct measurements (some firms measured multiple times, some firms with multiple divisions measured separately and rolled into one firm score)
- BSIMM4 continues to show that leading firms on average employ two full time software security specialists for every 100 developers
- BSIMM4 describes the work of 974 software security professionals working with a development-based satellite of 2039 people to secure the software developed by 218,286 developers

“We are very pleased with the effect BSIMM is having beyond its primary use as a reflection of the state of software security,” said Sammy Migues, co-author of the ongoing study and Cigital Principal. “We see it referenced directly in business partner discussions, in government and commercial acquisitions, in service level agreements, and vendor management processes.”

The fifty-one firms participating in the BSIMM Project make up the BSIMM Community. The BSIMM Community hosts a private mailing list and an annual Conference where representatives gather together in an off-the-record forum to discuss day to day administration of software security initiatives. In 2011, 21 of 42 firms participated in the second annual BSIMM Community Conference hosted in Washington State. And in Spring of 2012, the first BSIMM Europe Community conference held in Amsterdam included 17 firms with a presence in the European market.

“Fidelity Investments makes use of BSIMM measurements taken over time to identify areas for improvement in our software security initiative,” said David Smith, VP, Technology Risk Management, Fidelity. “Access to the BSIMM Community adds additional value both when trying to get new initiatives off the ground and when working to enhance and evolve existing initiatives. The BSIMM Community's industry leaders are knee deep in real-world software security, have a deep well of experience to draw on, and often have extremely effective initiatives well underway. As such, they provide valuable insight on how to succeed with software security at a world class level.”

For more information and to access the BSIMM4 study, which is distributed free of charge under a Creative Commons license, please visit: