New Methods in Automated XSS Detection & Dynamic Exploit Creation

All Material and Methods Contained Here Patent Pending Globally. All Rights Reserved.
xssWarrior.com
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New Methods in Automated XSS Detection
& Dynamic Exploit Creation
A Multi-deck Presentation
Kenneth F. Belva, CISSP, CEH
xssWarrior.com

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Contents & Deck Content
● Contact Information / Bio
● Slide Deck 1: Methods and Techniques Overview
– Describes the overall picture of how things work
● Slide Deck 2: OWASP AppSecUSA 2015 Presentation
– Gives more details about methods and variations
● Slide Deck 3: xssWarrior & XSS: A Basic Introduction
– Non-Technical Introduction with screenshots of product
showing this is not just theory / vaporware

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Ken's Contact Information
Email: contact @ xssWarrior.com
Product: http://xssWarrior.com
Twitter: http://twitter.com/xssWarrior
Me: http://twitter.com/infosecmaverick
Research: http://securitymaverick.com
Essays: http://www.bloginfosec.com
Stop by and say, 'Hi'!

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Bio of Kenneth F. Belva
Kenneth F. Belva is the Publisher and Editor-in-Chief of bloginfosec.com. He is current develops xssWarrior, currently the only scanner
than can automate testing for Stored XSS, for commercial use at xssWarrior.com. In addition, he is an independent penetration
tester and security researcher.
For the past 15 years he worked in Cyber Security mainly in the financial services vertical, most recently at a multinational
conglomerate, conducting both technical and non-technical risk assessments at the application and network layers. From 2005 -
2013 he managed an Information Technology Risk Management Program for a bank whose assets are Billions of dollars.
At the OWASP AppSec2013 conference BugCrowd validated three of his 0-day vulnerabilities he found in Yahoo, Yandex and Angelist
within the first two days of BugBash2013. He has since been credited with finding a number of other vulnerabilities on sites such as
Netflix and OKCupid.
He was previously on the board of the New York Metro Chapter of the Information Systems Security Association (ISSA) where he
served in various capacities over the past 9 years. He has spoken and moderated at the United Nations as well as presented on
AT&T’s Internet Security News Network (ISNN) on discovering unknown web application vulnerabilities as well as being
interviewed on security enablement.
ITsecurity.com recognized him as one of the top information security influencers in 2007.
In 2009, he was published in the Information Security Management Handbook, Sixth Edition, edited by Hal Tipton and Micki Krause. He
also co-authored one of the central chapters in Enterprise Information Security and Privacy, edited by Warren Axelrod, Jennifer L.
Bayuk and Daniel Schutzer.
He recently co-authored a paper entitled “Creating Business Through Virtual Trust: How to Gain and Sustain a Competitive Advantage
Using Information Security” with Sam Dekay of The Bank of New York. of security breaches on stock prices.
Mr. Belva frequently presents at information security conferences around the US as well as globally. He writes on day-to-day information
security experiences in a non-essay format at SecurityMaverick.com when time permits and can be followed on twitter
@infosecmaverick

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Slide Deck 1
Methods and Techniques Overview

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New Methods in Automated XSS Detection
& Dynamic Exploit Creation
xssWarrior.com

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Overview of Methods and Techniques
Presented at OWASP AppSecUSA 2015

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Points of Interest
● Please note: This presentation is a very simple
explanation to communicate the method and
concepts
● See OWASP presentation for more in-depth
ideas and examples
● Not vapor-ware: Advanced Scanner Exists
● Links on second to last slide for more information
● Please visit: xssWarrior.com

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Part 1:
The Current Automated Methodology

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Most Popular XSS Detection Methodology:
The Exploit String Includes the Payload/Token
<script>alert(12345)</script>
Scanners Slam Strings into Application
Hoping for a Callback or Event to Fire for
Validation
Inefficient and Inaccurate

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One Major Problem is Transformations
"script"alert12345"/script"
Most Popular XSS Detection Methods Cannot
Account for Different Exploit Situations

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Part 2:
The New Testing Methodology
Applies to All XSS:
Reflected, ReflectedStored, Stored, DOM

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Step 1: Tracing Data and Building Cases:
Inputs and Outputs
The goal:
Track where the data goes into the application and where it comes out
We assign a unique slug value to each field and load it into the application
Assign unique slug value to a field and submit
http://website?parm=1 -> http://website?parm=12345
Spider site to see where unique slugs come out in HTML/JS /DOM/etc.
In this way we build cases of input and output
Page 1 ---> Page 2 / Page 3 / Page 4
Example of Slug in HTML Output
<img src="12345" >some text</img>
<a href="a">12345</a>
We can inject custom script into DOM and search for our slug

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Step 2: Parse source where slug found to get
MINUMUM characters needed for each context
<img src="12345" >some text</img>
"> is needed for Case 1 Exploit and None Needed for Case 2 Exploit
Case 1:
<img src="12345">[exploit]</img>
Case 2:
<img src="[exploit.js]">some text</img>

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Step 3:
Use Sandwich Method to Determine Potential Vulnerability and
Build Table of Characters that Pass though App/Filter
Sandwich Method:
Enclose string to search between two unique slugs
12345"12345
12345<12345
As these unique strings are searchable
we will know if they come out the other side for our cases built in Step 1
http://website?parm=12345"12345
http://website?parm=12345<12345
Potential Vulnerability:
<img src="12345"12345" >some text</img>
<a href="a">12345<12345</a>
Not Vulnerable (in modern browsers):
<a href="a">12345<12345</a>

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Step 4: If potential vulnerability exists check
for exploit characters that fit the context
Case 1 HTML:
Exploit 1:
<img src="http://website/EvilJS.js" >some text</img>
Exploit 2:
<img src="EvilJS.js" >some text</img>
Potential Exploits & Special Characters:
http://website/EvilJS.js --> :/.
EvilJS.js --> .
Case 2 HTML:
<a href="a">12345<12345</a>
Exploit 1:
<script>alert(10)</script> --> <>()/
Exploit 2:
<script>String.fromCharCode(88,83,83)</script> --> <>()/.,

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Step 5:
From Built Table We Can Further Determine
Exploit Selection: Which Should Work & Which Should Fail
Based on Which Characters Make it Through Filter
(Accurately Determine Transformations)
Translation Name Value-Originally Value-Submit Value-Detect
ASCII < < <
HTML < < <
HTML-NoSemi " " &#x22
HTML-pre < < <
HTML-pre " " "
Value-Submit = Value Submitted to Application
12345<12345
12345<12345
12345"12345
Value-Detect = Value Searched in HTML/JS/DOM by Scanner
12345<12345
12345<12345
12345"12345
When Submitted The Character Should be tested with and without URL encoding since older
browser do not encode before submission
12345%2212345 → 12345”12345

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Step 6: Build Exploit with Proper Syntax and Test
(A Simple Example)
Assume Proper Characters Passed Filter and in our Table
HTML Case: <img src="12345" >some text</img>
Syntax from parsing: " >
Exploit: <script>alert(1)</script>
Dynamic Exploit: "><script>alert(1)</script>
Test / Submit & Scan: 12345"><script>alert(1)</script>12345
Result 1 (Valid): <img src="12345"><script>alert(1)</script>12345”>some text</img>
An Invalid Might look Like: <img src="12345"><>alert1</s>12345”>some text</img>
12345"><>alert1</s>12345 Does not Match 12345"><script>alert(1)</script>12345
Since we can parse the HTML/JavaScript/DOM (syntax) and know what gets through the filter
we can build complex dynamic XSS exploits

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Additional Notes
All Other String Combinations are Searchable.
For Example, Anti-XSS Libraries:
12345<script12345
12345<script>12345

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Part 3:
Additional Automated XSS Exploit Techniques

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Item 1: New Exploit Validation Method
without Callbacks or Event Trigger
If data is assigned a variable by definition the code has executed
Assume our exploit is:
<script> sploitValidationField = 12345 </script>
If we search for sploitValidationField in the DOM
and find the value in it is 12345
We will know our exploit will work
(Call backs and event triggers are still valid too)

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Item 2: Privilege Escalation Testing
Build Case in following way:
Authenticate and Load Slugs as User of one Level
(Input)
Authenticate as Higher Level user and Scan for Slugs
(Output)
Once Mapped from Lower to Higher User Test using
Above Methods

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Closing Remarks & Links
● Support Our Cyber Security Industry Independent Researchers:
– Please License: Don't Steal
● Currently Available as API and Service Offering
– http://xssWarrior.com
● LinkedIn Application Business Page
– https://www.linkedin.com/company/xsswarrior
● Contact information for Engagements and Speaking
– speak@xssWarrior.com
● Linkedin Profile
– https://www.linkedin.com/in/kenbelva
● xssWarrior YouTube Video:
– https://youtu.be/CxHvr9Et3lo
● OWASP AppSecUSA 2015
– https://appsecusa2015.sched.org/event/b3bf7e553d06f523704697068f0adedc
– https://www.youtube.com/playlist?list=PLpr-xdpM8wG93dG_L9QKs0W1cD-esQEzU

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Thank You Much For Your Time

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Slide Deck 2
OWASP AppSecUSA 2015 Presentation

New Methods in Automated XSS Detection:
Dynamic XSS Testing without Using Static Payloads
Kenneth F. Belva, CISSP
2015
http://xssWarrior.com
All Material and Methods Contained Here
Patent Pending. All Rights Reserved

On Payloads: Static /
Signature Analysis
Current Known &
Popular Automated
XSS Testing Methods
The Payload “Slam” The Tracing Payload
The Trace and then
Payload Replace
Issues with Payloads:
Syntax and
Transformations
Table of Contents
 Introduction / Background
 What this presentation is and what it is not....
 Some History: Discovering the Dynamic XSS
Methodologies
Part 1: The State of Automated XSS
Discovery Today

All Material and Methods Contained Here Patent Pending. All Rights Reserved

Table of Contents (pt2)
 Part 2: New Methods -
 Dynamic Analysis of XSS
Vulnerabilities: The Theory & (Some)
Practice
 Change of Focus from Payloads to Characters
 Application Component Review: Filters, DB, Memory, Source & DOM
 Let's briefly talk about slugs and fields
 Tracing and parsing for needed characters
 The Sandwich Method
 The New XSS Detection Logic
 A Quick Reflected XSS Example
 Sandwich Method Extended: Brute-Force, Special Strings, Various
Encodings & more
 Filtering in the field: A Real-life Pen Test Example
 The Questions of Accuracy and Efficiency
 Browser Considerations
 Goodbye Payloads! XSS is now about Characters, Slugs, Parsing & Filtering


 Part 2: New Methods
 Dynamic Analysis of XSS
Vulnerabilities: The Practice
 Spidering for Slugs and XSS
 HTTP Methods: GET / POST / HEADER /
COOKIES
 Another Simple Reflected XSS Example
 A Simple Stored XSS Detection Example
 A brief word on DOM-Based XSS


 Part 3: New Methods - Dynamic
XSS Exploitation


Introduction / Background


What this presentation is
& what it is not…
This presentation is a starter introduction to a new way of doing Dynamic XSS vulnerability detection
This presentation shows SIMPLE examples in order to communicate the UNDERLYING CONCEPTS of Dynamic
XSS Discovery
It does NOT cover every iteration of the methods described
• I briefly cover DOMbased XSS in this presentation but the methods described here can be extended for this as well – I will cover
some of these verbally
It does NOT cover more complex ideas and XSS cases but it should be understood from the presentation
how these may be pragmatically solved and implemented
The presentation covers straight HTML / JavaScript but it should also be understood that the methods
contained herein also apply to additional technologies such as Flash and ActiveX
It is NOT a product pitch
xssWarrior: The methodology presented herein is not theory. A real application exists that embodies this
presentation and it is continuing to be enhanced to add more and more functionality described here


Some History
 Discovering the Dynamic XSS
Methodologies
I used major
and open
source scanners
in large scale
environments
(20132014)
When the
current
automated
scanners
finished
processing I
would review
the sites
manually and I
could almost
always find
additional XSS
vulnerabilities
not found by
the scanners
I noticed that
the exploits
returned back
from these
scanners did not
always function
properly:
namely, I
needed to
correct the
syntax to get
them to execute
Valentines Day
2014 Yahoo!
offers a doubles
bounty for
sports.yahoo.co
m. Found XSS
Across 17
domains and
every page on
those domains.
Why didn't their
scanner(s) catch
it?
This lead me to
create an
improved
automated XSS
vulnerability
scanning
detection
system that can
find the types of
vulnerabilities I
was finding
manually before
I wrote a quick
prototype
scanner and
found a bunch
of XSS in
bounties using
the method I
developed
I subsequently
turned
prototype into a
full fledged
scanner
xssWarrior
which included
expanding my
original method
to include
Stored XSS &
DOMbased XSS
All material
contained
within is patent
pending


 Part 1:
 The State of Automated
 XSS Discovery Today


Almost all automated
scanners today use a
payload methodology
These strings consist of:
Sample exploits
Syntax
Sometimes these
strings contain an
identifier or tracer
value
Sometimes
callback /
debugging
payloads
Problem: The big issue is
that one needs a high
volume of use cases to
satisfy every single
variation
Satisfying all
variations is not
possible
Cannot handle
complex or unique
XSS issues
Problem: If it doesn't fit
something predefined it
isn't found
This is the XSS
equivalent to anti
virus signatures
Let's turn to a few Open
Source examples:
Please note I am a
big fan of OWASP
and their projects.
On Payloads
 Static / Signature Analysis


OWASP Xenotix XSS
Payloads


Sample Xenotix Payload
Variations


Other Tool Payloads
(XSSer)


Other Tool Payloads
(W3af)


Current Know & Popular
 Automated XSS Testing Methods
When searching out “in the wild” for XSS detection, all
methods found used payloads to some degree
Generally speaking there are only three distinct methods
•The rest appear to be a variation of the three
•Some combine different elements of the three
•This would include added predefined / static characters strings
into the front for syntax
•Clearly some of these methods will yield better results
When we examine the methods we will look at
•The underlying ideas behind the method
•The logic
•The elements / components of the payload
•How it all fits together in order to test for XSS


The Payload “Slam”
 Underlying Idea:
 Assign the variable's data value with a known payload
without anything else to it. Notice: no trace value
 The logic:
 http://vulnsite.com?param=DATAVALUE
 http://vulnsite.com?param=payload (signature)


The Tracing Payload
 Underlying Ideas:
 Put a tracer value in a known payload so the payload can be
tracked
 If we determine the payload executes, we know which one did
 The Logic:
 http://vulnsite.com?param=<payload>tracervalue</payload>
(signature)
 The trace value, such as 12345, is embedded in the predefined
payload. Example:
 http://vulnsite.com?param=<script>alert(12345)</script>


The Trace and then
Payload Replace
 Underlying Idea:
 Similar to the “Slam” but puts a tracevalue into the logic
 Assign the variable's data value with a tracevalue to
see if user supplied data return to the application
 If the tracevalue is returned, assigned a payload and
determine if vulnerable
 The Logic:
 http://vulnsite.com?param=tracervalue
 http://vulnsite.com?param=payload (signature)


Issue with Payloads
 Syntax and Transformations
Often times a filter will:
Eliminate
anything to right
of the “bad”
character
Reject the entire
string if it
contains a “bad”
character
Complex Script Tag Syntax
It needs to fit the
exact payload
syntax
We need to be able to
account for when data is
transformed: example,
from %27 to ' or x27 to '
Payloads will often fail
because they cannot
account for filtering
variations


 Part 2: New Methods
 Dynamic Analysis of XSS Vulnerabilities:
 The Theory & Practice


The Change of Focus
 from Payloads to Characters
The idea is that instead of using payloads we test each situation individually based on it's specific circumstances
• We do this by figuring out which characters need to be tested in any given situation (context and syntax)
The move from Payloads to Characters gives some distinct advantages
• We can figure out how the application interprets characters that are passed to it and, should there be filtering, figure out the rules of
the filter.
• We can narrow our requirements to exactly what the situation calls for and test only for those characters needed (derived from the
context and syntax)
• We can account for more complexity when the application does not fit a perdefined set of assumptions: we can figure out the unique
combination of characters and the correct syntax to define proper HTML/JavaScript/JSON/XML/etc. For example, a complex script tag.
• It allows for more fine grained testing
This process may be used in an automated system
With the characters and syntax information can dynamically discover XSS vulns, especially complex ones
With the character and syntax information can write custom exploits too
The key points:
• if we know what characters are needed for correct syntax and we know which characters get through the filter (and how to get them
through) there is an extremely high probability there is an vulnerability and in some cases we can know it 100%
• With this information we can then turn to validation of the vulnerability and test different ways (browser / character encodings /
specific strings / etc.) it may come about as well as write specific tests for the XSS issue found


Let`s briefly talk about
slugs and fields
 Assignment, Tracing, Tracking &
Syntax Parsing


Application Component
 Review: Filters, DB, Memory,
Source & DOM


The Sandwich Method
 Remember:
 can advantageously be automated
 tests any and every character and string combinations!
 Instead of using a single slug (such as 123456789), we use two in concert with one another
 Between the two trace slugs we can then place any additional character or string creating a
new unique string
 Examples (no spaces normally):
 123456789 A 123456789
 123456789 “ 123456789
 123456789 <script> 123456789
 123456789 ' 123456789
 123456789 %27 123456789
 Etc / etc / etc....
 If we detect the unique string in the output of the application we know our character or string
has made it through the application. For example, we test a URL encoded character:
 We submit to app string A:
123456789%27123456789
 We search output for string B: 123456789'123456789
 We know if we find string B in the output we know the ' has made it through the
application


The New Automated Dynamic
XSS Detection Logic
 Underlying Ideas:
 The goal is to determine the characters needed to complete the syntax needed for XSS
 We can then determine if the characters and strings needed for XSS make it through the application
 We can create variations based on specific scenarios and get accurate testing results instead of firing “blind”
 We can create encoding variations for different characters and determine if the output would be vulnerable
when interpreted by specific browser versions
 The Logic:
 http://vulnsite.com?param=WEBSITEVALUE
 <-- If tracervalue is returned somewhere in the application or found in the DOM we have a potential
vulnerability
 <-- Parse for syntax & determine HMTL/script/etc. characters needed
 <-- Parse for other elements such as tags to generate XSS exploits specific for that specific scenario
 http://vulnsite.com?param=tracervalue<character>tracervalue
 <--- Now we can test for special characters to see what gets through the filter
 <--- There can be a lot of variations on characters/strings that get tested/passed (character
encodings, known strings, etc.)
 http://vulnsite.com?param=tracervalue<payload (custom)>tracervalue
 <--- Payloads get created based on results of character and string testing
 <--- Possible but not always needed
 http://vulnsite.com?param=payload (custom)
 <--- Final result
 (Note we are now using custom values instead of payload signatures)


Sandwich Method
Extended
 Brute-Force, Special Strings,
Various Encodings & more
 (In reality: no spaces in the examples below)
 6ea261c8 <script 6ea261c8
 6ea261c8 <script> 6ea261c8
 6ea261c8 %3c 6ea261c8 (URL encode >)
 6ea261c8 9 6ea261c8 (Decimal: ')
 6ea261c8 ' 6ea261c8 (HTML Hex: ')
 6ea261c8 u0027 6ea261c8 (Unicode: ')
 6ea261c8 x27 6ea261c8 (Straight Hex: ')


Filtering in the field
A Real-life Pen Test Example
 Case 1:
 < did not work
 %3c did not work
 %%3c WORKED
 Case 2:
 javascript did not work (it was filtered)
 ' did not work (it was filtered)
 java'script did work: turned into → javascript
 And we can test for these cases because we are testing for characters and
strings without using payloads!


The Questions of Accuarcy
And Efficiency
For most fields we only need to check the characters that make up the syntax (and any encoding variations
we choose to run)
Therefore: we check fewer characters than the payload method which usually checks all payloads for a
parameter
• This is especially true if we determine that one of the essential characters needed for the syntax fails: we don't need to continue
checking the additional characters. Example: a double quote needed in an HTML attribute
If we like we can add additional characters we plan to use in our exploit to determine which exploit to use or
how we need to build it (based on the context / syntax analysis). Examples:
• If we use String.fromCharCode we may want to add , () .
• Or if we decide to use data:text/html;base64 in an href we may need to add :/;
Extremely accurate
• If the strings don't match we know character didn't make it through
• If we don't find that the essential syntax characters, strings and / or our exploit characters pass we know it will not be vulnerable
We can analyze more complex issues


Browser Considerations
Once we know the characters that
pass through the application, we
can build strings that are browser
specific if we know that &#; will
make it through but something
like < will not
We can get strings through that
would be interpreted differently
on different browsers
This means we can test for XSS
per browser and not just generic,
perhaps IE8 is vulnerable but not
IE10 or FireFox 35, etc.


Goodbye Payloads
 XSS is about Characters, Slugs,
Parsing & Filtering
Key Takeaways!
• Figure out how the application works via character
determination is more advantageous than “blindly”
submitting payload strings
• We can figure how the application behaves by
using the sandwich method to trace character and
string data to figure out how the application will
behave: filter and / or transform data
• Using the character & syntax data is more accurate
and efficient
• We can use the character & syntax data to
determine if a vulnerability or potentially
vulnerability exists and then create custom exploits
especially when the syntax is complex.
• We can use the sandwich method to test for
characters and strings in other circumstances even
if we cannot parse the source: Flash, ActiveX, etc.


Part 2: New Methods
Dynamic Analysis of XSS Vulnerabilities:
The Practice


“Spidering” for slugs and
XSS
In reality any number of methods can be used to get URLs (especially for “AJAX URLs”)– for ease of
discussion we will stick with spidering
•If they are immediately found after the page submission we have a Reflected XSS
•If they are submitted but found on another page (in the same session) we have InMemory XSS
•If they are found after the session is cleared and a new one is formed we have Stored XSS
•We find our slugs referenced in the immediate page in the client memory (DOMbased)
Whatever method is used, when spidering the application the components search for slugs
If these slugs are found, they are recorded and associated with the location they were inputted
The goal is to find places to input but also find where slugs are outputted
We map the input to output of the slugs: this may be a 1 to Many relationship, especially when
dealing with Stored XSS (think a name field)
Once we have the input and then the output we can test which characters go in and come out using
the Sandwhich Method.
We can then track the results and the one's that have vulnerabilities based on characters and
syntax we can being generating exploits.


Testing Application
Methods & Synataxes
We can use the
sandwich and
detection methods
described above to
test different
methods and parts
of the application
• GET / POST / HEADER
/ COOKIES
The application can
also test for
different syntax
formats and test
those
• JSON / HTML / XML /
Etc.


A bried word on
DOM-Based XSS
We can search through
the DOM for the slug
We can then search
through the DOM for the
slug sandwich and
determine the characters
can be represented / not
filtered or transformed
We can determine what
strings / exploits can be
represented in the DOM
We can then used various
validation methods –
such as callbacks, debug,
etc. – to test exploits


Part 3: New Methods
A Brief Method for Dynamic XSS Exploitation


Issues with Current Static
XSS Exploit Payloads
 The issue is that the payload is the exploit
 It is not customized for the context / syntax
 It could transform due to a filter but there still may be a
vulnerability
 Introducing Dynamic XSS Exploit Analysis and Generation
 By knowing the characters and the context a customized
exploit may be developed for specific situation, including
accounting for transformations of characters through the filter
 (see pen testing example earlier %%3c)


Method to Determine and
Create Custom XSS Exploit (pt1)
 Recall our testing logic:
 http://vulnsite.com?param=WEBSITEVALUE
 <-- If tracervalue is returned somewhere in the application or found in the
DOM we have a potential vulnerability
 <-- Parse for syntax & determine HMTL/script/etc. characters needed
 <-- Parse for other elements such as tags to generate XSS exploits specific
for that specific scenario
 http://vulnsite.com?param=tracervalue<character>tracervalue
 <--- Now we can test for special characters to see what gets through the
filter
 <--- There can be a lot of variations on characters/strings that get
tested/passed (character encodings, known strings, etc.)
 http://vulnsite.com?param=tracervalue<payload (custom)>tracervalue
 <--- Payload based on results of testing
 <--- Possible but not always needed
 http://vulnsite.com?param=payload (custom)
 <--- Final result


Method to Determine and
Create Custom XSS Exploit (pt2)
 A Simple Dynamic Custom XSS Exploit Method
 Step 1: Find Slug in HTML
 Step 2: Parse HTML to determine where CheckSum exists / syntax check
 Step 3: Determine characters needed to pass through filter based on HTML Syntax
 Step 4: Use XSS Test Method to determine characters that pass through filter
 Step 5: If characters pass through filter, build exploit string based on characters
and context and then check if exploit string passes through filter
 Step 6: (optional) Exploit string can be out of band callback for extra validation
 Step 7: Remove MD5 Check Sum and Save Exploit
 Based on the characters and syntax needed, we may decide to add special
characters to test which we most likely would use in the exploit we plan to use
 We can technically make this determination either after we test the
preliminary characters
 That is to say, after we determine if the necessary characters get through
via step Step 3
 Or, we can “guess” and add them to Step 3 and test everything “at once”


Writing the Dynamic
Exploit
 We can make it more complex depending on the
different exploits for the context: – html tag / text or
attribute / script / etc.
 For instance, in the body tag:
 If we can pass “=() we might be able to exploit
 onload="exploit()"
 Where we might not be able to pass “</>()
 “><script>alert(10)</script>”<
 We can account for the transformation and / or
filtering mechanisms in place in the application
 < will not make it through but %% does


Q&A


Ken`s Contact Information
Email: contact@xssWarrior.com
Product: http://xssWarrior.com
Twitter: http://twitter.com/xssWarrior
Me: http://twitter.com/infosecmaverick
Research: http://securitymaverick.com
Essays: http://www.bloginfosec.com
Stop by and say, 'Hi'!


Bio of Kenneth F.Belva
Kenneth F. Belva is the Publisher and Editor-in-Chief of bloginfosec.com. He is current develops xssWarrior, currently the only scanner
than can automate testing for Stored XSS, for commercial use at xssWarrior.com. In addition, he is an independent penetration tester and
security researcher.
For the past 15 years he worked in Cyber Security mainly in the financial services vertical, most recently at a multinational conglomerate,
conducting both technical and non-technical risk assessments at the application and network layers. From 2005 - 2013 he managed an
Information Technology Risk Management Program for a bank whose assets are Billions of dollars.
At the OWASP AppSec2013 conference BugCrowd validated three of his 0-day vulnerabilities he found in Yahoo, Yandex and Angelist
within the first two days of BugBash2013. He has since been credited with finding a number of other vulnerabilities on sites such as
Netflix and OKCupid.
He was previously on the board of the New York Metro Chapter of the Information Systems Security Association (ISSA) where he served
in various capacities over the past 9 years. He has spoken and moderated at the United Nations as well as presented on AT&T’s Internet
Security News Network (ISNN) on discovering unknown web application vulnerabilities as well as being interviewed on security
enablement.
ITsecurity.com recognized him as one of the top information security influencers in 2007.
In 2009, he was published in the Information Security Management Handbook, Sixth Edition, edited by Hal Tipton and Micki Krause. He
also co-authored one of the central chapters in Enterprise Information Security and Privacy, edited by Warren Axelrod, Jennifer L. Bayuk
and Daniel Schutzer.
He recently co-authored a paper entitled “Creating Business Through Virtual Trust: How to Gain and Sustain a Competitive Advantage
Using Information Security” with Sam Dekay of The Bank of New York. of security breaches on stock prices.
Mr. Belva frequently presents at information security conferences around the US as well as globally. He writes on day-to-day information
security experiences in a non-essay format at SecurityMaverick.com when time permits and can be followed on twitter @infosecmaverick


xssWarrior.com
26
Slide Deck 3
xssWarrior & XSS: A Basic Introduction

xssWarrior.com
27
xssWarrior & XSS:
A Basic Introduction

xssWarrior.com
28
xssWarrior & XSS
● Presented at One of World's Top Cyber Sec Conferences
● What are some of the consequences of XSS?
● How is it different? What are some benefits?
● Some Public Results
● Graphical Interfaces
● Conclusion
● Who Am I?
● Contact Information

xssWarrior.com
29
What are some of the the
consequences of XSS?
● Log in as another person (session stealing)
● Install malware such as APTs (Advanced
Persistent Threats) on the user visiting the
compromised website
● Redirect users to a fake / malicious website
under attacker's control

xssWarrior.com
30
How is it different?
What are some benefits?
● xssWarrior uses a proprietary method to test and detect for XSS
vulnerabilities
● Finds difficult XSS vulnerabilities in complex code
● The scanner excels at a notorious difficult XSS issue: Stored XSS
– Up to now most scanners cannot test for this accurately due to the limitations of
the current techniques
The Benefits:
● With the new automated process, the application lowers the total cost to
find XSS vulnerabilities
● Tool easily fits into existing automated scanning processes and
procedures

xssWarrior.com
31
Some Public Results
● Patent-Pending Technique used to find XSS vulnerabilities on following
Bug Bounty programs
– Netflix
– Yahoo
– OKCupid
– Yandex
● xssWarrior found XSS in below applications resulting in CVEs
– CVE-2014-6635 – Exponent CMS
– CVE-2014-6618 – Your online shop
– CVE-2014-6619 – Pizza Inn
– [To be assigned] – TomatoCart
– CVE-2015-2043 – MyConnection Server 8.2b

xssWarrior.com
32

xssWarrior.com
33
Graphical Interface

xssWarrior.com
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Results Part 1

xssWarrior.com
35
Results Part 2

xssWarrior.com
36
Conclusion
● Use xssWarrior to find common and hard to find
XSS vulnerabilities in web properties
● Protect the infrastructure by finding security
holes before bad guys do (defense)
● Find XSS holes in adversaries websites before
they do (offense)

xssWarrior.com
37
Who Am I?
● I am almost 20 year veteran in the cyber security
field
● Had technical and managerial roles in the cyber
space: currently developing xssWarrior for public
release
● Active in NYC cyber scene: prior 8+ year board
member of NYC chapter of ISSA
● Presented at NYC chapters of OWASP, ISSA, ISC2
and ASIS

New Methods in Automated XSS Detection & Dynamic Exploit Creation

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New Methods in Automated XSS Detection & Dynamic Exploit Creation