Self-XSS (Cross Site Scripting) ~ Social Engineering Attack and Prevention

Self-XSS (Cross Site Scripting) ~ Social Engineering Attack and Prevention

Last time , I have explained about the Clickjacking attack and prevention.  Today,  i am going to explain about the Self-XSS(Cross Site Scripting) Attack

What is Self-XSS?

Self-XSS is one of the popular Social Engineering Attack used by Attackers to trick users into paste the malicious code in browser.  Results in attacker accessing to the whatever website you visit. Usually scammers use this attack for tricking users to buy products or get money through online survey .

Recently, Hackers Attacked Facebook with explicit hardcore porn images. Facebook says it might be self-Xss Attack .

Javascript can be executed in browser url bar.
For example , enter the following code in your browser:

javascript:alert('kotharavichandra');

This will show a pop up box with "kotharavichandra".  An attacker can use this for malicious purpose. He can steal Confidential data, cookies, redirect to malware sites and more.
For Eg:
Entering the following code will display the cookies in your browser:

javascript:alert("Cookies:"+document.cookies+"  "+"\n By \n kotharavichandra");

The above code is not going to anything maliciously other than displaying the cookies.  But an attacker can extend the script so that it can take advantage your data.

Security Tips from kotharavichandra:

• Use NoScript add on that will prevent javascript running in your browser.
• Don't click the shorthand urls for Example: bit.ly/55ewEb?22.  This may redirect to an infected sites. 

Aware of Social Engineering:

• If anyone ask you(even if he is your friend) to paste the scripts in browser bar, Never do this mistake.  
• If anyone says "Iphone only $10", Don't eager to click it. 
• If anyone says "1000 shares will cure a baby", Never do this mistake. Facebook shares never help to get money or help to cure baby.
• Read our EHN spam report to know the latest updates about the facebook scams.

God give us the Sixth Sense,Use it and think before you click any links or following the other instructions.

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What is Clickjacking Attack? How to Prevent? | UI Redressing

What is Clickjacking Attack? How to Prevent? | UI Redressing

Will answering simple maths quiz delete your Social Network account?  If your answer is "No", then check this news Linkedin Clickjacking Vulnerability and come back.  Will visiting a website turn on your webcam? The answer is "Yes".  Check this Flash player clickjacking vulnerability.

If you read above news completely, It will be easy for you to understand  what is clickjacking.  Ok, lets continue to our Article.

Clickjacking also known as UI Redressing,is one of Malicious Technique tricking users to click the button/image that will run hidden malicious script from another site.

An attacker uses multiple transparent or opaque layers to trick a user into clicking on a button or link on another page when they were intending to click on the the innocuous page. Thus an attacker hijack the click to another website.  That's why it is known as Clickjacking(Click+Hijacking).  The term "clickjacking" was coined by Jeremiah Grossman and Robert Hansen in 2008.

Example:

Lets take the real time example "Linkedin clickjacking vulnerability.

The above image may look like simple maths problem.  Once you click the submit button, it will delete your Linkedin account(if you are logged in) without asking any questions.

Clickjacking Attack can be used for:

• Tricking users to turn on their webcam and microphone using this adobe vulnerability (this security flaw fixed by adobe)
• Getting more Twitter Followers
• Post in your facebook wall.
• Can delete your profile.

Prevention Techniques:

Client Side(Security tips for users):

Flash Player:

Update your Flash Player(old version are vulnerable to Clickjacking). 

Browser Security Addons: 

Noscript:
Noscript is Mozilla add on that provides protection against clickjacking,XSS and other malicious scripts.  Noscript is available for mobiles also.

Comitari Web Protection Suite: Comitari provides client side protection against ClickJacking (aka UI Redressing) attacks. Installed as browser add-on

GuardedID: It is a commercial product which provides client-side clickjack protection for users of IE or Firefox without interfering with the operation of legitimate iFrames

Server Side( For Developers)

Frame Killer:

Framekiller is javascript snippet that can be used in webpage  to avoid inserting frames from different sources.  This can provide security against frame based clikjacking.

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Bypassing the XSS Filters : Advanced XSS Tutorials for Web application Pen Testing

Bypassing the XSS Filters : Advanced XSS Tutorials for Web application Pen Testing

copyrights reserved ©kotharavichandra.blogspot.com

Hi friends, last time, i explained what is XSS and how an attacker can inject malicious script in your site. As i promised earlier, i am writing this advanced XSS tutorial for you(still more articles will come).

Sometimes, website owner use XSS filters(WAF) to protect against XSS vulnerability.
For eg: if you put the

<scirpt>alert("hi")</scirpt>

, the Filter will escape the "(quote) character , so the script will become

<script>alert(>xss detected<)</script>

Now this script won't work. Likewise Filters use different type of filtering method to give protection against the XSS.  In this case, we can use some tricks to bypass the filter.  Here i am going to cover that only.

1.Bypassing magic_quotes_gpc

The magic_quotes_gpc=ON is a PHP setting(configured in PHP.ini File) , it escapes the every ' (single-quote), " (double quote) and \  with a backslash automatically. For Eg:

<scirpt>alert("hi");</scirpt>

will be filtered as

<script>alert(\hi\)</script>

.so the script won't work now.

This is well known filtering method, but we can easily bypass this filter by using ASCII characters instead.
For Eg:

alert("hi");</scirpt>
can be converted to
String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 104, 105, 34, 41, 59)

so the script will become .  In this case there is no "(quotes) or '(single quotes) or / so the filter can't filter this thing.  Yes, it will successfully run the script.

String.fromCharCode() is a javascript function that converts ASCII value to Characters.

How to convert to ASCII values?

There are some online sites that converts to ASCII character. But i suggest you to use Hackbar Mozilla addon .

After installing hackbar add on ,press F9.  It will open the small box above the url bar. click the XSS->String.fromCharCode()

Now it will popup small window. enter the code for instance alert("Hi").  click ok button.  Now we got the output.

copy the code into the inside and insert in the vulnerable sites

For eg: 

hxxp://vulnerable-site/search?q=<script>String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 104, 105, 34, 41, 59)</script>

2.HEX Encoding

we can encode our whole script into HEX code so that it can't be filtered.
For example:<script>alert("Hi");</script>

can be convert to HEX as:
%3c%73%63%72%69%70%74%3e%61%6c%65%72%74%28%22%48%69%22%29%3b%3c%2f%73%63%72%69%70%74%3eNow put the code in the vulnerable site request.
For ex:

hxxp://vulnerable-site/search?q=%3c%73%63%72%69%70%74%3e%61%6c%65%72%74%28%22%48%69%22%29%3b%3c%2f%73%63%72%69%70%74%3e

 Converting to HEX:
This site will convert to hex code: http://centricle.com/tools/ascii-hex/

3.Bypassing using Obfuscation

Some website admin put the script,alert in restricted word list.  so whenever you input this keywords, the filter will remove it and will give error message like "you are not allowed to search this". This can bypassed by changing the case of the keywords(namely Obfuscation). 
For eg:

<script>ALeRt("hi");</script>

This bypass technique rarely works but giving trial is worth.

4. Closing Tag

Sometimes putting "> at the beginning of the code will work.

<script>alert("Hi");</script>

This will end the previous opened tag and open our script tag.
Example:

hxxp://vulnerable-site/search?q="><script>alert("Hi");</script>

Conclusion:

From above article, it is clear that XSS filters alone not going to protect a site from the XSS attacks. If you really want to make your site more secure, then ask PenTesters to test your application or test yourself.

Also there are lot of different filter bypassing technique, i just covered some useful techniques for you.

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