wdiff rfc7034.original rfc7034.txt

WEBSEC
Internet Engineering Task Force (IETF) D. Ross
Internet-Draft
Request for Comments: 7034 Microsoft
Intended status:
Category: Informational T. Gondrom
Expires: February 28, 2014
ISSN: 2070-1721 Thames Stanley
August 27,
October 2013

HTTP Header Field X-Frame-Options
draft-ietf-websec-x-frame-options-12

Abstract

To improve the protection of web applications against Clickjacking, clickjacking,
this definition document describes the X-Frame-Options HTTP response header
field that field, which
declares a policy policy, communicated from the server to the client browser on
browser, regarding whether the browser may display the transmitted
content in frames that are part of other web pages. This
informational document serves to document the existing use and
specification of this X-Frame-Options HTTP response header field.

Status of This Memo

This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a maximum candidate for any level of Internet
Standard; see Section 2 of RFC 5741.

Information about the current status of six months this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on February 28, 2014.
http://www.rfc-editor.org/info/rfc7034.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. X-Frame-Options Header . . . . . . . . . . . . . . . . . . . 3 . 4
2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3 . 4
2.2. Augmented Backus-Naur Form (ABNF) . . . . . . . . . . . . 5
2.2.1. Examples of X-Frame-Options . . . . . . . . . . . . . 5 6
2.3. Design Issues . . . . . . . . . . . . . . . . . . . . . . 5 6
2.3.1. Enable HTML content Content from other domains Other Domains . . . . . . . . 6
2.3.2. Browser Behaviour Behavior and Processing . . . . . . . . . . . 6
2.3.2.1. Violation of X-Frame-Options . . . . . . . . . . . 6
2.3.2.2. Variation in current browser behaviour Current Browser Behavior . . . . . 6 . 7
2.3.2.3. Usage design pattern Design Pattern and example scenario Example Scenario for
the ALLOW-FROM parameter . Parameter . . . . . . . . . . . . . 8
2.3.2.4. No caching Caching of the X-Frame-Options header Header . . . . . 8
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4.1.
3.1. Registration Template . . . . . . . . . . . . . . . . . . 9
5.
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5.1.
4.1. Privacy Considerations . . . . . . . . . . . . . . . . . . 10
6.
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1.
5.1. Normative References . . . . . . . . . . . . . . . . . . . 10
6.2.
5.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Browsers that support That Support X-Frame-Options . . . . . . . 12 . 13
Appendix B. Description of a Clickjacking attack Attack . . . . . . . . 12 13
B.1. Shop . . . . . . . . . . . . . . . . . . . . . . . . . . 12 . 13
B.2. Online Shop Confirm Purchase Page . . . . . . . . . . . . 12 13
B.3. Flash Configuration . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . .
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 13

1. Introduction

In 2009 and 2010 2010, many browser vendors ([Microsoft-X-Frame-Options],
[CLICK-DEFENSE-BLOG], and [Mozilla-X-Frame-Options]) introduced the
use of a non-standard HTTP [RFC2616] header field "X-Frame-Options"
to protect against Clickjacking clickjacking [Clickjacking]. HTML-based web
applications can embed or "frame" other web pages. Clickjacking is a
type of attack that occurs when an attacker uses multiple transparent
or opaque layers in the user interface to trick a user into clicking
on a button or link on another page from server B when they were
intending to click on the same place of the overlaying page from
server A. Thus, the attacker is "hijacking" clicks meant for their page A
and routing them to another page B. The attacker is tricking the user (who
sees the overlaying user interface content from page A) into clicking
specific locations on the underlying page from server B, triggering
some actions on server B and potentially using an existing session
context in that step. This is an attack on both the user and on
server B. And In addition, server A may or may not be the attacker.

This specification provides informational documentation about the
current use and definition of the X-Frame-Options HTTP header field.
As described in Section 2.3.2.2 2.3.2.2, not all browsers implement X-Frame-
Options exactly
X-Frame-Options in exactly the sames same way, which can lead to unintended
results. And And, given that the "X-" construction is deprecated
[RFC6648], the X-Frame-Options header field will be replaced in the
future be
replaced by the Frame-Options directive in the Content Security Policy Version
(CSP) version 1.1 [CSP-1-1].

Existing anti-ClickJacking

A study [FRAME-BUSTING] demonstrated that existing anti-clickjacking
measures, e.g. Frame-breaking Javascript, e.g., frame-breaking JavaScript, have weaknesses so that allow
their protection can to be circumvented as a
study [FRAME-BUSTING] demonstrated. circumvented.

Short of configuring the browser to disable frames and script scripts
entirely, which massively impairs browser utility, browser users are
vulnerable to this type of attack.

The use of "X-Frame-Options" allows a web page from host B to declare
that its content (for example example, a button, links, text, etc.) must not
be displayed in a frame (<frame> or <iframe>) of another page (e.g. (e.g.,
from host A). This is done by a policy declared in the HTTP header
and enforced by browser implementations as documented here.

1.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].

2. X-Frame-Options Header

The X-Frame-Options HTTP response header field indicates a policy on that
specifies whether the browser should render the transmitted resource
within a <frame> or an <iframe>. Servers can declare this policy in
the header of their HTTP responses to prevent clickjacking attacks, and by this
ensuring
which ensures that their content is not embedded into other pages or
frames.

2.1. Syntax

The header field name is:

X-Frame-Options

There are three different values for the header field. These values
are mutually exclusive, exclusive; that is is, the header field MUST be set to
exactly one of the three values MUST
be set. values.

DENY
A browser receiving content with this header field MUST NOT
display this content in any frame.

SAMEORIGIN
A browser receiving content with this header field MUST NOT
display this content in any frame from a page of different origin
than the content itself.

If a browser or plugin can not cannot reliably determine whether or not
the origin of the content and the frame have are the same origin, same, this MUST be
treated as "DENY".

Please note that current implementations vary on the
interpretation of this criteria: criteria. In some some, it only allows a page
to be framed if the origin of the top-level browsing-context browsing context is
identical to the origin of the content using the X-FRAME-
OPTIONS X-Frame-Options
directive; in others others, it may consider the origin of the framing
page instead. See also section Also see Section 2.3.2.2 for more details on the
nesting of frames and variations in the handling of this header
field by different browsers. And In addition, refer to
section 5 Section 4,
paragraph 2 for the resulting potential security problems.

ALLOW-FROM (followed by a serialized-origin [RFC6454])
A browser receiving content with this header MUST NOT display this
content in a frame from any page with a top-level browsing context
of different origin than the specified origin. While this can
expose the page to risks by the trusted origin, in some cases cases, it
may be necessary to allow the framing by content from other
domains.

The meaning of the term "serialized-origin" is given in [RFC6454].
If the ALLOW-FROM value is used, it MUST be followed by a valid
origin [RFC6454] (as a subset of the URI [RFC3986]) [RFC3986]).

Any data beyond the domain address (i.e. (i.e., any data after the "/"
separator) is to be ignored. And the The algorithm to compare origins from
[RFC6454] SHOULD be used to verify that a referring page is of the
same origin as the content (in the case of SAMEORIGIN) or that the
referring page's origin is identical with the ALLOW-FROM
serialized-origin serialized-
origin (in the case of ALLOW-FROM). Though in conflict with
[RFC6454], current implementations do not consider the port as a
defining component of the origin. I.e. origin; i.e., existing implementations
differ with [RFC6454] in that origins with the same protocol but
different port values are considered equivalent.

Wildcards or lists to declare multiple domains in one ALLOW-FROM
statement are not permitted (see Section 2.3.2.3).

2.2. Augmented Backus-Naur Form (ABNF)

The RFC 5234 [RFC5234] ABNF of the X-Frame-Options header field value
is the following. following:

X-Frame-Options = "DENY"
/ "SAMEORIGIN"
/ ( "ALLOW-FROM" RWS SERIALIZED-ORIGIN )

RWS = 1*( SP / HTAB )
; required whitespace

With

with serialized-origin as defined in [RFC6454] and the definition of
RWS (required whitespace) is the same required
whitespace (RWS) as defined in [HTTPbis-P1].

RWS is used when at least one linear whitespace octet is required to
separate field tokens. RWS SHOULD be generated as a single space
(SP). Multiple RWS octets that occur within field-content SHOULD
either be replaced with a single SP or transformed to all SP octets before
interpreting the field value or forwarding the message downstream.

And

SP (space) and HTAB (horizontal tab) horizontal tab (HTAB) are as defined in Appendix B.1 of RFC
5234
[RFC5234], Appendix B.1. [RFC5234].

The values are specified as ABNF strings, and therefore strings; therefore, they are case-
insensitive.

2.2.1. Examples of X-Frame-Options

X-FRAME-OPTIONS:

X-Frame-Options: DENY

X-FRAME-OPTIONS:

X-Frame-Options: SAMEORIGIN

X-FRAME-OPTIONS:

X-Frame-Options: ALLOW-FROM https://example.com/

2.3. Design Issues

2.3.1. Enable HTML content Content from other domains Other Domains

There are a number of main direct vectors that enable HTML content
from other domains domains, and browser implementations of X-Frame-Options
cover all of them:

o IFRAME tag

o Frame tag

o The Object tag (requires a redirect)

o Applet tag

o Embed tag

Besides these, other ways to host HTML content can be possible. For
example
example, some plugins may host HTML views directly. If these plugins
appear essentially as frames (as opposed to top-level windows), the
plugins must conform to the X-FRAME-OPTIONS X-Frame-Options policy as specified in
this document as well.

2.3.2. Browser Behaviour Behavior and Processing

To allow secure implementations, browsers must behave in a consistent
and reliable way.

If an X-Frame-Options HTTP header field prohibits framing, the user- user
agent of the browser MAY immediately abort downloading or parsing of
the document.

2.3.2.1. Violation of X-Frame-Options

When a browser discovers that loaded content with the X-FRAME-OPTIONS X-Frame-Options
header field would be displayed in a frame against the specified
orders of the header, the browser SHOULD redirect to a "NOFRAME" page
as soon as possible
to a "No-Frame" page. possible. For example example, this can be a noframe.html page
that also states the full URL and hostname of the protected page.

The NoFrame NOFRAME page could provide the user with an option to open the
target URL in a new window.

Implementations of this vary, vary: some browsers will show a message that
allows the user to safely open the target page in a new window.
Other window,
whereas other implementations will simply render an empty frame.

2.3.2.2. Variation in current browser behaviour Current Browser Behavior

There are currently variations in the implementation of the X-FRAME-
OPTIONS
X-Frame-Options header. For example example, not all browsers support the "ALLOW-
FROM"
"ALLOW-FROM" option. "ALLOW-FROM" was initially an Internet Explorer
extension and and, at the time of writing writing, has not been uniformly
implemented by other user agents.

Furthermore

Furthermore, the criteria for the SAMEORIGIN (and ALLOW-FROM)
directive may not be evaluated unanimously either: The the known
implementations in Appendix A evaluate the SAMEORIGIN directive based
on the origin of the framed page and the top-level browsing-context, browsing context,
while other implementations might evaluate it based on the framed
page and the framing page, or the whole chain of nested frames inbetween. in
between.

To illustrate the difference between the comparison with of the "framing
page" and the "top-level browsing-context" browsing context", consider the following
scenario: Web web pages may embed frames with other pages which that, in turn turn,
embed frames with other pages as well well, and so on. In theory theory, this
can result in an infinite nesting of framed pages. For example example, web
page A may contain in a frame web page B, B in a frame, and web page B contains in a
frame may contain
web page C. C in a frame.

Web page A
<html>
....
<frame src="https://URI_of_web_page_B" />
</html>

Web Page page B
<html>
....
<frame src="https://URI_of_web_page_C" />
</html>

And

and so forth... forth.

In this example, for the nested frames with the inner framed inner-framed web page
C, the most outer web page A would be the "top-level browsing-
context" browsing
context", and web page B would be the "framing page" page".

These potential variations in the evaluation of the header by
different implementations impair the useage usage and reliability of this
http
HTTP header and have security implications as described in section 5. Section 4.
A revised version of x-frame-options X-Frame-Options in the form of a frame-options Frame-Options
directive in the CSP 1.1[CSP-1-1] 1.1 [CSP-1-1] will unify the behaviour behavior, and it is
expected that newer implementations will use it rather than the
mechanisms documented here.

2.3.2.3. Usage design pattern Design Pattern and example scenario Example Scenario for the ALLOW-FROM
parameter
Parameter

As the "ALLOW-FROM" field only supports one serialized-origin, in
cases when the server wishes to allow more than one resource to frame
its content, the following design pattern can fulfil fulfill that need:

1. A page that wants to render the requested content in a frame
supplies its own origin information to the server providing the
to-be-framed
content to be framed via a querystring query string parameter.

2. The Server server verifies that the hostname meets its criteria criteria, so that
the page can be is allowed to be framed by the target resource. This
may
may, for example example, happen via a look-up lookup of a white-list whitelist of trusted
domain names that are allowed to frame the page. For example,
for a Facebook "Like" button, the server can check to see that
the supplied hostname matches the hostname(s) expected for that
"Like" button.

3. The server returns the hostname in X-FRAME-OPTIONS: ALLOW-FROM "X-Frame-Options: ALLOW-FROM"
if the proper criteria was met in step #2.

4. The browser enforces the X-FRAME-OPTIONS: ALLOW-FROM "X-Frame-Options: ALLOW-FROM" header.

2.3.2.4. No caching Caching of the X-Frame-Options header

It is not recommended to cache Header

Caching the X-Frame-Options header for a
resource. resource is not recommended.
Caching the X-Frame-Options response could result in problems
because:

1. The browser has to check for For every http-request of the resource resource, the browser has to check
whether the X-Frame-Options header has been set and then act
accordingly, as a resource itself might be created dynamically
and the header could change with it, too.

2. And also, Also, as outlined in section 2.3.2.3., Section 2.3.2.3, servers may generate X
-Frame-Options
X-Frame-Options header responses depending on the request.
Example case: Considering that we have only one serialized-origin
in the ALLOW-FROM directive, imagine a user has multiple pages
open in his browser tabs with one of web page 1 from domain A and
the second of web
page 2 from domain B, and both frame the same page from domain C
with the ALLOW-FROM directive. In that case case, the page needs to
reply to both requests with different X-Frame-
Options X-Frame-Options headers,
with the first pointing to origin A, A and the second pointing to
origin B.

However, we found that none of the major browsers listed in
Appendix A cache the responses.

3. Acknowledgements

This document was derived from input from specifications published by
various browser vendors such as Microsoft (Eric Lawrence, David
Ross), Mozilla, Google, Opera and Apple.

4. IANA Considerations

This memo is a request to

IANA to include has included the specified HTTP header in the "Permanent Message
Header Field Name" registry as outlined in Registration "Registration Procedures
for Message Header Fields [RFC3864]

4.1. Fields" [RFC3864].

3.1. Registration Template

PERMANENT MESSAGE HEADER FIELD REGISTRATION TEMPLATE:

Permanent Message Header Field Names Template:

Header field name: X-Frame-Options

Applicable protocol: http [RFC2616]

Status: informational

Author/Change Informational

Author/change controller: IETF

Specification document(s): draft-ietf-websec-x-frame-options RFC 7034

Related information:

Figure 1

5. None

4. Security Considerations

The introduction of the X-FRAME-OPTIONS http X-Frame-Options HTTP header field does
improve improves
the protection against Clickjacking. clickjacking. However, it is not
self-sufficient on its own self-
sufficient enough to protect against all kinds of these attack
vectors. It must be used in conjunction with other security measures
like secure coding (e.g. (e.g., input validation, output encoding,
...) etc.)
and the Content Security Policy version 1.0 [CSP].

It is important to note that current implementations do not check the
origins of the framing resources' entire ancestor tree of frames of the framing
resources, frames, and
this may expose the resource to attack in multiple-
nested multiple-nested scenarios.

The browser implementations evaluate based on the origin of the
framed page and the top-level browsing-context (i.e. browsing context (i.e., the most outer
frame):

If a resource from origin A embeds untrusted content from origin B,
that untrusted content can embed another resource from origin A with
an X-Frame-Options: SAMEORIGIN policy "X-Frame-Options: SAMEORIGIN" policy, and that check would pass
when the user agent only verifies the top-level browsing context.
Therefore
Therefore, web developers should be aware that embedding content from
other sites can leave their web pages vulnerable to clickjacking even
if the X-Frame-Options header is used.

Furthermore, X-Frame-Options must be sent as an HTTP header field and
is explicitly ignored by user agents when declared with a meta http-
equiv
http-equiv tag.

5.1.

4.1. Privacy Considerations

There are two kinds of potential data leakage to consider:

1. Using X-FRAME-OPTIONS X-Frame-Options with the parameter ALLOW-FROM allows a page
to guess or infer information about who is framing it. A web
server may answer requests with the X-FRAME-OPTIONS ALLOW-FROM "X-Frame-Options: ALLOW-FROM"
header and by thus determine which other page is framing it. This
is inherent by design, but it may lead to data leakage data-leakage or data data-
protection concerns.

2. The web server using the ALLOW-FROM directive may disclose to
other parties who request effectively
discloses the page origin specified in the header by which page it
is allowed to be framed. header. If a web server
wishes to reduce this leakage, it is recommended to generate the
ALLOW-FROM header for each request based on the design pattern as
described in section Section 2.3.2.3.

5. References

6.1.

5.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.

[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.

[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
December 2011.

6.2.

5.2. Informative References

[CLICK-DEFENSE-BLOG]
Microsoft, "Clickjacking Defense", 2009, <http://
blogs.msdn.com/b/ie/archive/2009/01/27/ie8-security-part-
vii-clickjacking-defenses.aspx>.

[CSP-1-1] Barth, A. and M. West, "Content
Lawrence, E., "IE8 Security Policy 1.1", W3C
Working Draft WD-CSP11-20130604, June 2013,
<http://www.w3.org/TR/2013/WD-CSP11-20130604/>.

Latest version available at Part VII: Clickjacking
Defenses", Microsoft Developer Network Blogs,
January 2009, <http://blogs.msdn.com/b/ie/archive/2009/01/
27/ie8-security-part-vii-clickjacking-defenses.aspx>.

[CSP] Sterne, B. and A. Barth, "Content Security Policy 1.0",
W3C Candidate Recommendation CR-CSP-20121115,
November 2012,
<http://www.w3.org/TR/2012/CR-CSP-20121115/>.

Latest version available at

[CSP-1-1] Barth, A. and M. West, "Content Security Policy 1.1", W3C
Working Draft WD-CSP11-20130604, June 2013,
<http://www.w3.org/TR/2013/WD-CSP11-20130604/>.

[CSRF] OWASP (Open Web Application Security Project), "OWASP
Top-10: Cross-Site "Top-10
2013-A8-Cross-Site Request Forgery (CSRF)", 2010, <https:/
/www.owasp.org/index.php/Top_10_2013-A8-Cross-
Site_Request_Forgery_%28CSRF%29>. June 2013,
<https://www.owasp.org/index.php/
Top_10_2013-A8-Cross-Site_Request_Forgery_%28CSRF%29>.

[Clickjacking]
OWASP (Open Web Application Security Project),
"Clickjacking", 2010, April 2013,
<http://www.owasp.org/index.php/Clickjacking>.

[FRAME-BUSTING]
Stanford Web Security Research, "Busting frame busting: a
study of clickjacking vulnerabilities at popular sites",
July 2010,
<http://seclab.stanford.edu/websec/framebusting/>.

[HTTPbis-P1]
IETF,
Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", 2013, <http://tools.ietf.org/html/
draft-ietf-httpbis-p1-messaging-23>. Work in Progress,
July 2013.

[Microsoft-X-Frame-Options]
Microsoft,
Lawrence, E., "Combating ClickJacking With X-Frame-Options", X-Frame-
Options", Microsoft Developer Network Blogs, March 2010, <http://blogs.msdn.com/b/ieinternals/archive/2010/03
/30/combating-clickjacking-with-x-frame-options.aspx>.
<http://blogs.msdn.com/b/ieinternals/archive/2010/03/30/
combating-clickjacking-with-x-frame-options.aspx>.

[Mozilla-X-Frame-Options]
Mozilla,
Mozilla Developer Network, "The X-Frame-Options response
header", 2010,
<https://developer.mozilla.org/en-US/docs/The_X-FRAME-
OPTIONS_response_header>. August 2013, <https://developer.mozilla.org/
en-US/docs/The_X-FRAME-OPTIONS_response_header>.

[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004.

[RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham,
"Deprecating the "X-" Prefix and Similar Constructs in
Application Protocols", BCP 178, RFC 6648, June 2012.

Appendix A. Browsers that support That Support X-Frame-Options

o Internet Explorer 8+

o Firefox 3.6.9+

o Opera 10.5+

o Safari 4+

o Chrome 4.1+

Appendix B. Description of a Clickjacking attack

More Attack

A more detailed explanation of Clickjacking clickjacking scenarios follows.

B.1. Shop

An Internet Marketplace/Shop marketplace/shop offering a feature with a link/button to
"Buy this" Gadget
The marketplace gadget wants their affiliates (who could be malicious
attackers) to be able to stick the "Buy such-and-such such and such from XYZ"
IFRAMES into their pages. There is a possible Clickjacking clickjacking threat
here, which is why the marketplace/onlineshop marketplace/online shop needs to then
immediately navigate the main browsing context (or a new window) to a
confirmation page which that is protected by anti-Clickjacking anti-clickjacking protections.

B.2. Online Shop Confirm Purchase Page

The "Confirm Purchase" page of an online shop must be shown to the
end user
end-user without the risk of an overlay or misuse by an attacker.
For that reason, the confirmation page uses a combination of anti-
CSRF
anti-CSRF (Cross Site Request Forgery, Forgery [CSRF]) tokens and the X-FRAME-
OPTIONS
X-Frame-Options HTTP header field, mitigating ClickJacking clickjacking attacks.

B.3. Flash Configuration

Macromedia Flash configuration settings are set by a Flash object
which
that can run only from a specific configuration page on Macromedia's
site. The object runs inside the page and thus can be subject to a
ClickJacking
clickjacking attack. In order to prevent ClickJacking clickjacking attacks
against the security settings, the configuration page uses the X
-FRAME-OPTIONS
X-Frame-Options directive.

Appendix C. Acknowledgements

This document was derived from input from specifications published by
various browser vendors such as Microsoft (Eric Lawrence and David
Ross), Mozilla, Google, Opera, and Apple.

Authors' Addresses

David Ross
Microsoft
U.S.

EMail: dross@microsoft.com

Tobias Gondrom
Thames Stanley
Kruegerstr. 5A
Unterschleissheim
Germany

Phone: +44 7521003005
Email:

EMail: tobias.gondrom@gondrom.org