Xss Cheat Sheet Github

/ Comments off



This cheat sheet is focused on providing developer guidance on Clickjack/UI Redress attack prevention.

# xss-cheat-sheet # Basics Xss. HTML Context - Simple Tag Injection. Gunakan saat input masuk ke dalam nilai atribut dari tag HTML atau tag luar kecuali. Yang dijelaskan dalam kasus berikutnya. Tambahkan '-' ke payload jika input masuk dalam komentar HTML. ' HTML Context - In Block Tag Injection. This cross-site scripting (XSS) cheat sheet contains many vectors that can help you bypass WAFs and filters. You can select vectors by the event, tag or browser and a proof of concept is included for every vector. You can download a PDF version of the XSS cheat sheet. This cheat sheet was brought to by PortSwigger Research. Follow us on twitter to recieve updates.

The most popular way to defend against Clickjacking is to include some sort of 'frame-breaking' functionality which prevents other web pages from framing the site you wish to defend. This cheat sheet will discuss two methods of implementing frame-breaking: first is X-Frame-Options headers (used if the browser supports the functionality); and second is javascript frame-breaking code.

The frame-ancestors directive can be used in a Content-Security-Policy HTTP response header to indicate whether or not a browser should be allowed to render a page in a <frame> or <iframe>. Sites can use this to avoid Clickjacking attacks by ensuring that their content is not embedded into other sites.

frame-ancestors allows a site to authorize multiple domains using the normal Content Security Policy semantics.

Content-Security-Policy: frame-ancestors Examples

Common uses of CSP frame-ancestors:

  • Content-Security-Policy: frame-ancestors 'none';
    • This prevents any domain from framing the content. This setting is recommended unless a specific need has been identified for framing.
  • Content-Security-Policy: frame-ancestors 'self';
    • This only allows the current site to frame the content.
  • Content-Security-Policy: frame-ancestors 'self' '*.somesite.com' 'https://myfriend.site.com';
    • This allows the current site, as well as any page on somesite.com (using any protocol), and only the page myfriend.site.com, using HTTPS only on the default port (443).

Note that the single quotes are required.

See the following documentation for further details and more complex examples:

Limitations

  • Browser support: CSP frame-ancestors is not supported by all the major browsers yet.
  • X-Frame-Options takes priority:Section 'Relation to X-Frame-Options' of the CSP Spec says: 'If a resource is delivered with an policy that includes a directive named frame-ancestors and whose disposition is 'enforce', then the X-Frame-Options header MUST be ignored', but Chrome 40 & Firefox 35 ignore the frame-ancestors directive and follow the X-Frame-Options header instead.

The X-Frame-Options HTTP response header can be used to indicate whether or not a browser should be allowed to render a page in a <frame> or <iframe>. Sites can use this to avoid Clickjacking attacks, by ensuring that their content is not embedded into other sites. Set the X-Frame-Options header for all responses containing HTML content. The possible values are 'DENY', 'SAMEORIGIN', or 'ALLOW-FROM uri'

X-Frame-Options Header Types

There are three possible values for the X-Frame-Options header:

  • DENY, which prevents any domain from framing the content. The 'DENY' setting is recommended unless a specific need has been identified for framing.
  • SAMEORIGIN, which only allows the current site to frame the content.
  • ALLOW-FROM uri, which permits the specified 'uri' to frame this page. (e.g., ALLOW-FROM http://www.example.com).
    • Check limitations below because this will fail open if the browser does not support it.
    • Other browsers support the new CSP frame-ancestors directive instead. A few support both.

Browser Support

The following browsers support X-Frame-Options headers.

References:

  • X-Frame-Options Compatibility Test - Check this for the LATEST browser support info for the X-Frame-Options header

Implementation

To implement this protection, you need to add the X-Frame-Options HTTP Response header to any page that you want to protect from being clickjacked via framebusting. One way to do this is to add the HTTP Response Header manually to every page. A possibly simpler way is to implement a filter that automatically adds the header to every page or to add it at Web Application Firewall of Web/Application Server level.

Cheat

Common Defense Mistakes

Meta-tags that attempt to apply the X-Frame-Options directive DO NOT WORK. For example, <meta http-equiv='X-Frame-Options'> will not work. You must apply the X-FRAME-OPTIONS directive as HTTP Response Header as described above.

Limitations

  • Per-page policy specification: The policy needs to be specified for every page, which can complicate deployment. Providing the ability to enforce it for the entire site, at login time for instance, could simplify adoption.
  • Problems with multi-domain sites: The current implementation does not allow the webmaster to provide a whitelist of domains that are allowed to frame the page. While whitelisting can be dangerous, in some cases a webmaster might have no choice but to use more than one hostname.
  • ALLOW-FROM browser support: The ALLOW-FROM option is a relatively recent addition (circa 2012) and may not be supported by all browsers yet. BE CAREFUL ABOUT DEPENDING ON ALLOW-FROM. If you apply it and the browser does not support it, then you will have NO clickjacking defense in place.
  • Multiple options not supported: There is no way to allow the current site and a 3rd party site to frame the same response. Browsers only honour one X-Frame-Options header and only one value on that header.
  • Nested Frames don't work with SAMEORIGIN and ALLOW-FROM: In the following situation, the http://framed.invalid/child frame does not load because ALLOW-FROM applies to the top-level browsing context, not that of the immediate parent. The solution is to use ALLOW-FROM in both the parent and child frames (but this prevents the child frame loading if the //framed.invalid/parent page is loaded as the top level document).
  • X-Frame-Options Deprecated While the X-Frame-Options header is supported by the major browsers, it was never standardized and has been deprecated in favour of the frame-ancestors directive from the CSP Level 2 specification.
  • Proxies Web proxies are notorious for adding and stripping headers. If a web proxy strips the X-Frame-Options header then the site loses its framing protection.

One way to defend against clickjacking is to include a 'frame-breaker' script in each page that should not be framed. The following methodology will prevent a webpage from being framed even in legacy browsers, that do not support the X-Frame-Options-Header.

In the document HEAD element, add the following:

Xss Cheat Codes

First apply an ID to the style element itself:

Then, delete that style by its ID immediately after in the script:

This way, everything can be in the document HEAD and you only need one method/taglib in your API.

Reference:

The use of X-Frame-Options or a frame-breaking script is a more fail-safe method of clickjacking protection. However, in scenarios where content must be frameable, then a window.confirm() can be used to help mitigate Clickjacking by informing the user of the action they are about to perform.

Invoking window.confirm() will display a popup that cannot be framed. If the window.confirm() originates from within an iframe with a different domain than the parent, then the dialog box will display what domain the window.confirm() originated from. In this scenario the browser is displaying the origin of the dialog box to help mitigate Clickjacking attacks. It should be noted that Internet Explorer is the only known browser that does not display the domain that the window.confirm() dialog box originated from, to address this issue with Internet Explorer insure that the message within the dialog box contains contextual information about the type of action being performed. For example:

Consider the following snippet which is NOT recommended for defending against clickjacking:

This simple frame breaking script attempts to prevent the page from being incorporated into a frame or iframe by forcing the parent window to load the current frame's URL. Unfortunately, multiple ways of defeating this type of script have been made public. We outline some here.

Double Framing

Some frame busting techniques navigate to the correct page by assigning a value to parent.location. This works well if the victim page is framed by a single page. However, if the attacker encloses the victim in one frame inside another (a double frame), then accessing parent.location becomes a security violation in all popular browsers, due to the descendant frame navigation policy. This security violation disables the counter-action navigation.

Victim frame busting code:

Attacker top frame:

Xss Cheat Sheet Pdf

Attacker sub-frame:

The onBeforeUnload Event

A user can manually cancel any navigation request submitted by a framed page. To exploit this, the framing page registers an onBeforeUnload handler which is called whenever the framing page is about to be unloaded due to navigation. The handler function returns a string that becomes part of a prompt displayed to the user.

Say the attacker wants to frame PayPal. He registers an unload handler function that returns the string 'Do you want to exit PayPal?'. When this string is displayed to the user is likely to cancel the navigation, defeating PayPal's frame busting attempt.

The attacker mounts this attack by registering an unload event on the top page using the following code:

PayPal's frame busting code will generate a BeforeUnload event activating our function and prompting the user to cancel the navigation event.

No-Content Flushing

While the previous attack requires user interaction, the same attack can be done without prompting the user. Most browsers (IE7, IE8, Google Chrome, and Firefox) enable an attacker to automatically cancel the incoming navigation request in an onBeforeUnload event handler by repeatedly submitting a navigation request to a site responding with '204 - No Content'.

Navigating to a No Content site is effectively a NOP, but flushes the request pipeline, thus canceling the original navigation request. Here is sample code to do this:

Exploiting XSS filters

IE8 and Google Chrome introduced reflective XSS filters that help protect web pages from certain types of XSS attacks. Nava and Lindsay (at Blackhat) observed that these filters can be used to circumvent frame busting code. The IE8 XSS filter compares given request parameters to a set of regular expressions in order to look for obvious attempts at cross-site scripting. Using 'induced false positives', the filter can be used to disable selected scripts. By matching the beginning of any script tag in the request parameters, the XSS filter will disable all inline scripts within the page, including frame busting scripts. External scripts can also be targeted by matching an external include, effectively disabling all external scripts. Since subsets of the JavaScript loaded is still functional (inline or external) and cookies are still available, this attack is effective for clickjacking.

Victim frame busting code:

Attacker:

The XSS filter will match that parameter <script>if to the beginning of the frame busting script on the victim and will consequently disable all inline scripts in the victim's page, including the frame busting script. The XSSAuditor filter available for Google Chrome enables the same exploit.

Clobbering top.location

Several modern browsers treat the location variable as a special immutable attribute across all contexts. However, this is not the case in IE7 and Safari 4.0.4 where the location variable can be redefined.

IE7: Once the framing page redefines location, any frame busting code in a subframe that tries to read top.location will commit a security violation by trying to read a local variable in another domain. Similarly, any attempt to navigate by assigning top.location will fail.

Victim frame busting code:

Attacker:

Safari 4.0.4

Rsnake Xss Cheat Sheet

We observed that although location is kept immutable in most circumstances, when a custom location setter is defined via defineSetter (through window) the object location becomes undefined.

The framing page simply does:

Now any attempt to read or navigate the top frame's location will fail.

Restricted zones

Most frame busting relies on JavaScript in the framed page to detect framing and bust itself out. If JavaScript is disabled in the context of the subframe, the frame busting code will not run. There are unfortunately several ways of restricting JavaScript in a subframe:

In IE 8:

In Chrome:

Firefox and IE:

Activate designMode in parent page.

Jim Manico - jim@owasp.org

Santhosh Tuppad - santhosh.tuppad@gmail.com

Jeffrey Walton

Till Maas

Dave Wichers - dwichers@gmail.com

Michael Brook

Tom Parker

Xss cheat codes

Shruti kulkarni

Yozo

Eelgheez

Aabashkin

This year SigSegv qualifiers are back,

You are tasked to steal the cookie from a web page. The target machine is running “Chrome with recent updates”, so it is advisable to test it in chrome.

You have one URL to test your payloads and the other one to validate your flag. The validation page will pass the link to a bot which will trigger XSS.

Finding injection point

Since there is no obvious forms or input elements apparent, we look at the page source ( follow comments for my thought proccess ) :

Xss Cheat Sheet Github 2019

The getUrlParam function takes url parameter layout and puts it inside “injection” element of the webpage. Queries such as ` http://qual-challs.rtfm.re:8080/?layout=YOURSTRINGHERE ` will render on the page.

However there is pesky DOMPurify.sanitize(layout); getting in our way of triggering the desired alert(1) box.After giving automated tools a try ( XSStrike and Burpsuite) and trying to concatenate some form of <script>alert(222)</script> to render on the page I kept getting owned by the sanitizer.

Alternatives from XSS cheat sheets [1] ,2 didn’t seem to work. However my friend point me to an interesting resource - DOMPurify bypass.

Bypassing DOMPurify

There is an excellent write-up describing a recent vulnerability in DOMPurify, that uses browsers auto-fix feature to close the tags of HTML elements that are not properly matching.

More on this behaviour here : https://research.securitum.com/dompurify-bypass-using-mxss/

So the PoC payload referenced in the article looks like this :

<svg></p><style><a> However it uses both img and onerror tags stripped by NuclearSanitizer(), so we can look once again at the cheat sheets and find other components that could do the trick.

?layout=<svg></p><style><a> With this I popped the first alert. DOMPurify is bypassed. Great, now to make it run without interaction and onto exfiltration. In this part you can get creative.

To steal the cookie, you need to make a request to a domain you control. A convenient web service for that is “Requestbin” [3] , which allows you to receive requests on their servers.

document.cookie is where a cookie is stored. We append it to the end of source URL, thus making the element call our server, with the cookie as a parameter. We catch this request in logs.

?layout=<svg></p><style><a>

Once we submit the full URL into the validator, a HTTP request is made to our cookie receiver server :

Cross Site Scripting Cheat Sheet Github

flag=sigsegv{pur1fy_mY_s0ul}

This was a fun challenge, and I got to learn XSS the fun way.

P.S.: Did you know that markdown in GithubPages runs any JS , including unescaped<script>alert('boxes')</script> , well now you know.

[1] Web Security Academy XSS cheat sheet https://portswigger.net/web-security/cross-site-scripting/cheat-sheet

Owasp Xss Cheat Sheet Github

[2] Payload ALL the things XSS repo https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XSS%20Injection

[3] Requestbin https://requestbin.com/