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Client-side JavaScript Vulnerabilities


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Automatically detecting client side JavaScript vulnerabilities using IBM Rational AppScan and JavaScript Security Analyzer (hybrid analysis)

Automatically detecting client side JavaScript vulnerabilities using IBM Rational AppScan and JavaScript Security Analyzer (hybrid analysis)

Published in: Technology
  • nice
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  • I guess I don't understand. You can manually execute any javascript from the client anyway just by typing 'javascript:{...}' in the address bar of any modern browser and the webkit browsers have a console where you can type and execute your own javascript commands, so if one wanted to call APIs from his own client, he could easily do it without js injection....

    I guess someone could create a malicious link as in the examples, but http could be configured not to run cross domains so you can't extract any information from any http request. Most sites require authentication before you access sensitive information anyway, so for the 'attack' to have any effect you would have to be logged in in one tab and then click on a link in another that redirects you back to a hacked page on the first, which would be a strange thing to do.
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  • FYI - JSA has been improved greatly recently, and now actually located that 40% of the F500 web sites are actually vulnerable!
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  • 1. Client-side JavaScript
    Security vulnerabilities
    The Twilight Zone of Web Application Security
    Ory Segal
    Security Products Architect, Rational
  • 2. ORY SEGAL
    Security products architect, Rational
    AppScan product manager
    Web Application Security Consortium officer
    Contributor (WASC, MITRE, NIST, OWASP)
    Renowned application security expert
  • 3. From server to client side – The migration story of web application logic
  • 4. 1990
    Capable of presenting only text and hyperlinks
    Embedded images in web pages (3rd. Party allowed)
    JavaScript enables programmatic modifications to HTML
    Embeds a page within a page (3rd party contents)
    Embed an Adobe Flash file for animation
    Client-side API (e.g. JS). Send & receive HTTP traffic programmatically, without refreshing the entire page
    Fetch data asynchronously using XHR reducing the time spent waiting on page loads. Desktop app look & feel
    Canvas, Media, Offline storage, D&D, Geolocation, Local SQL, …
    HTML5 &
  • 5. Logic is Migrating from Server to Client…
    We counted server-side vs. client-side LoC in popular web applications in 2005 and in 2010
  • 6. Client-side JavaScript Security Issues
  • 7. DOM-Based Cross-site Scripting
    A type of XSS (the third type after “Reflected” & “Stored”)
    Application doesn’t need to echo back user input like in Type I & Type II
    We poison a DOM element, which is used in JavaScript code
    1:<HTML>2: <TITLE>Welcome!</TITLE>3: Hi4: <SCRIPT>5: var pos = document.URL.indexOf("name=") + 5;
    6: document.write(document.URL.substring(pos,document.URL.length));
    7: </SCRIPT> <BR/>8: Welcome to our system
    Source : document.URL
    Sink : document.write()
    Results : document.write("Ory")
  • 8. DOM-Based Cross-site Scripting
    Attack Example<script>alert('hacked')</script>
    1: <HTML>2: <TITLE>Welcome!</TITLE>3: Hi4: <SCRIPT>5: var pos = document.URL.indexOf("name=") + 5;
    6: document.write(document.URL.substring(pos,document.URL.length));
    7: </SCRIPT> <BR/>8: Welcome to our system
    9: </HTML>
    Source : document.URL
    Sink : document.write()
    Results : document.write("<script>alert('hacked')</script>")
    • The attack took place entirely on the client-side (# fragment identifier)
    • 9. Hacker controlled DOM elements may include: document.URL, document.location, document.referrer, window.location, etc.
  • Client-side Open Redirect
    JavaScript code automatically redirects the browser to a new location
    New location is taken from a DOM element (URL, Query, Referrer, etc.)
    12: varsData =;
    13: varsPos = sData.indexOf("url=") + 4;
    14: varePos = sData.indexOf("&", sPos);
    15: varnewURL;
    16: if (ePos< 0) { newURL = sData.substring(sPos);}
    17: else { newURL = sData.substring(sPos, ePos);}
    18:window.location.href = newURL;
    Source : document.location
    Sink : window.location.href
    Results : window.location.href = "";
  • 10. Stored DOM-Based Cross-Site Scripting
    Exploiting HTML5 localStorage API
    17: var pos = document.URL.indexOf("name=") + 5;
    18: varyourName = document.URL.substring(pos,document.URL.length)
    19: decodeURI(yourName);
    20: = yourName;
    21: }
    3: <div id="header"></div>
    4: <script>
    5: varelem = document.getElementById("header");
    6: varname =;
    7: elem.innerHTML = "Hello, " + name;
    8: </script>
    Source : document.URL
    Storage :
    Sink : elem.innerHTML
    Results : elem.innerHTML = <value_of_name_parameter>
  • 11. So, how common are client-side JavaScript issues?
  • 12. (Lack of) Statistics on Client-Side JS Issues
    Two options for gathering statistics
    Automated discovery
    Manual discovery
    Automated tools
    Dynamic analysis tools only uncover ~30%
    Static analysis tools struggle with dynamic code (AJAX)
    Manual code review is hell – have you seen JavaScript lately?
    dojo._xdReset();if(dojo["_xdDebugQueue"]&&dojo._xdDebugQueue.length>0){dojo._xdDebugFileLoaded();}else{dojo._xdNotifyLoaded();}};dojo._xdNotifyLoaded=function(){for(var _99 in dojo._xdInFlight){if(typeofdojo._xdInFlight[_99]=="boolean"){return;}}
    dojo._inFlightCount=0;if(dojo._initFired&&!dojo._loadNotifying){dojo._callLoaded();}};if(typeof window!="undefined"){dojo.isBrowser=true;dojo._name="browser";(function(){var d=dojo;if(document&&document.getElementsByTagName){var _9a=document.getElementsByTagName("script");var _9b=/dojo(.xd)?.js(W|$)/i;for(vari=0;i<_9a.length;i++){varsrc=_9a[i].getAttribute("src");if(!src){continue;}var m=src.match(_9b);if(m){if(!d.config.baseUrl)
    {d.config.baseUrl=src.substring(0,m.index);}varcfg=_9a[i].getAttribute("djConfig");if(cfg){var _9c=eval("({ "+cfg+" })");for(var x in _9c){dojo.config[x]=_9c[x];}}break;}}}d.baseUrl=d.config.baseUrl;var n=navigator;vardua=n.userAgent,dav=n.appVersion,
    tv=parseFloat(dav);if(dua.indexOf("Opera")>=0){d.isOpera=tv;}if(dua.indexOf("AdobeAIR")>=0){d.isAIR=1;}d.isKhtml=(dav.indexOf("Konqueror")>=0)?tv:0;d.isWebKit=parseFloat(dua.split("WebKit/")[1])||undefined;d.isChrome=parseFloat(dua.split("Chrome/")[1])||undefined;d.isMac=dav.indexOf("Macintosh")>=0;var _9d=Math.max(dav.indexOf("WebKit"),dav.indexOf("Safari"),0);if(_9d&&!dojo.isChrome)
    {d.isSafari=parseFloat(dav.split("Version/")[1]);if(!d.isSafari||parseFloat(dav.substr(_9d+7))<=419.3){d.isSafari=2;}}if(dua.indexOf("Gecko")>=0&&!d.isKhtml&&!d.isWebKit){d.isMozilla=d.isMoz=tv;}if(d.isMoz){d.isFF=parseFloat(dua.split("Firefox/")[1]||dua.split("Minefield/")[1])||undefined;}if(document.all&&!d.isOpera){d.isIE=parseFloat(dav.split("MSIE ")[1])||undefined;var _9e=document.documentMode;if(_9e&&_9e!=5&&Math.floor(d.isIE)!=_9e){d.isIE=_9e;}}if(dojo.isIE&&window.location.protocol==="file:") {dojo.config.ieForceActiveXXhr=true;}d.isQuirks=document.compatMode=="BackCompat";d.locale=dojo.config.locale||(d.isIE?n.userLanguage:n.language).toLowerCase();
  • 13. Introducing JavaScript Security Analyzer
  • 14. What is JSA?
    1st and only to auto-detect client-side issues such as:
    DOM-based XSS
    Phishing through Open Redirect
    HTML5 Notification API Phishing
    HTML5 Web Storage API Poisoning
    HTML5 Client-side SQL Injection
    HTML5 Client-side Stored XSS
    HTML5 Web Worker Script URL Manipulation
    Email Attribute Spoofing
    /* analysis */
  • 15. Using JavaScript Security Analyzer
    Zero configuration required
  • 16. 16
    Viewing JSA Results in AppScan Standard
    AppScan Standard – Scan Results
    Vulnerable URL and line of code
    Tainted data flow information
  • 17. Lets try again…How common are client-side JavaScript issues?
  • 18. Using JSA we ran a research on real sites
    Fortune 500
    175 Most popular sites
    Non-obtrusive automated review
    Manually verified results
    Scary outcome…
  • 19. 14.5% Vulnerable
    169,443 Total Pages
    90,929 Unique Pages
    1659 Pages with Vulnerabilities
    Likelihood for a web page to be vulnerable is 1 : 55
  • 20. Who wrote these vulnerabilities?
    In house
    3rd Party
    • Marketing campaign JavaScript snippets
    • 21. Flash embedding JavaScript snippets
    • 22. Social networking JavaScript snippets
    • 23. Deep linking JavaScript libraries for Flash and AJAX applications
  • Issue Distribution
    DOM-based XSS
    Open Redirect
  • 24. JavaScript is becoming prominent
    Modern applications HTML5 AJAX Web2.0
    Application logic is shifting to client-side
    More code == more vulnerabilities
    Happens when code relies on parts of the DOM that are hacker-controlled
    Detection requires tedious manual work
    AppScan with JSA can automate client-side issues detection
  • 25. Q & A
  • 26. Thank You
    You can download the full whitepaper at: