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# defusedxml -- defusing XML bombs and other exploits

[![Latest Version](https://img.shields.io/pypi/v/defusedxml.svg)](https://pypi.org/project/defusedxml/)

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> "It's just XML, what could probably go wrong?"



Christian Heimes \<\>



## Synopsis



The results of an attack on a vulnerable XML library can be fairly

dramatic. With just a few hundred **Bytes** of XML data an attacker can

occupy several **Gigabytes** of memory within **seconds**. An attacker

can also keep CPUs busy for a long time with a small to medium size

request. Under some circumstances it is even possible to access local

files on your server, to circumvent a firewall, or to abuse services to

rebound attacks to third parties.



The attacks use and abuse less common features of XML and its parsers.

The majority of developers are unacquainted with features such as

processing instructions and entity expansions that XML inherited from

SGML. At best they know about `` from experience with HTML but

they are not aware that a document type definition (DTD) can generate an

HTTP request or load a file from the file system.



None of the issues is new. They have been known for a long time. Billion

laughs was first reported in 2003. Nevertheless some XML libraries and

applications are still vulnerable and even heavy users of XML are

surprised by these features. It's hard to say whom to blame for the

situation. It's too short sighted to shift all blame on XML parsers and

XML libraries for using insecure default settings. After all they

properly implement XML specifications. Application developers must not

rely that a library is always configured for security and potential

harmful data by default.






Table of Contents






## Attack vectors



### billion laughs / exponential entity expansion



The [Billion Laughs](https://en.wikipedia.org/wiki/Billion_laughs)

attack -- also known as exponential entity expansion --uses multiple

levels of nested entities. The original example uses 9 levels of 10

expansions in each level to expand the string `lol` to a string of 3 \*

10 9 bytes, hence the name "billion laughs". The resulting

string occupies 3 GB (2.79 GiB) of memory; intermediate strings require

additional memory. Because most parsers don't cache the intermediate

step for every expansion it is repeated over and over again. It

increases the CPU load even more.



An XML document of just a few hundred bytes can disrupt all services on

a machine within seconds.



Example XML:



    

    

    

    

    ]>

    &d;



### quadratic blowup entity expansion



A quadratic blowup attack is similar to a [Billion

Laughs](https://en.wikipedia.org/wiki/Billion_laughs) attack; it abuses

entity expansion, too. Instead of nested entities it repeats one large

entity with a couple of thousand chars over and over again. The attack

isn't as efficient as the exponential case but it avoids triggering

countermeasures of parsers against heavily nested entities. Some parsers

limit the depth and breadth of a single entity but not the total amount

of expanded text throughout an entire XML document.



A medium-sized XML document with a couple of hundred kilobytes can

require a couple of hundred MB to several GB of memory. When the attack

is combined with some level of nested expansion an attacker is able to

achieve a higher ratio of success.



    

    ]>

    &a;&a;&a;... repeat



### external entity expansion (remote)



Entity declarations can contain more than just text for replacement.

They can also point to external resources by public identifiers or

system identifiers. System identifiers are standard URIs. When the URI

is a URL (e.g. a `http://` locator) some parsers download the resource

from the remote location and embed them into the XML document verbatim.



Simple example of a parsed external entity:



    

    ]>

    &ee;



The case of parsed external entities works only for valid XML content.

The XML standard also supports unparsed external entities with a

`NData declaration`.



External entity expansion opens the door to plenty of exploits. An

attacker can abuse a vulnerable XML library and application to rebound

and forward network requests with the IP address of the server. It

highly depends on the parser and the application what kind of exploit is

possible. For example:



-   An attacker can circumvent firewalls and gain access to restricted

    resources as all the requests are made from an internal and

    trustworthy IP address, not from the outside.

-   An attacker can abuse a service to attack, spy on or DoS your

    servers but also third party services. The attack is disguised with

    the IP address of the server and the attacker is able to utilize the

    high bandwidth of a big machine.

-   An attacker can exhaust additional resources on the machine, e.g.

    with requests to a service that doesn't respond or responds with

    very large files.

-   An attacker may gain knowledge, when, how often and from which IP

    address an XML document is accessed.

-   An attacker could send mail from inside your network if the URL

    handler supports `smtp://` URIs.



### external entity expansion (local file)



External entities with references to local files are a sub-case of

external entity expansion. It's listed as an extra attack because it

deserves extra attention. Some XML libraries such as lxml disable

network access by default but still allow entity expansion with local

file access by default. Local files are either referenced with a

`file://` URL or by a file path (either relative or absolute).

Additionally, lxml's `libxml2` has catalog support. XML catalogs like

`/etc/xml/catalog` are XML files, which map schema URIs to local files.



An attacker may be able to access and download all files that can be

read by the application process. This may include critical configuration

files, too.



    

    ]>

    &ee;



### DTD retrieval



This case is similar to external entity expansion, too. Some XML

libraries like Python's xml.dom.pulldom retrieve document type

definitions from remote or local locations. Several attack scenarios

from the external entity case apply to this issue as well.



    

    

    

        

        text

    



## Python XML Libraries



| kind                                   | sax           | etree         | minidom       | pulldom       | xmlrpc        |

|----------------------------------------|---------------|---------------|---------------|---------------|---------------|

| billion laughs                         | **Maybe** (1) | **Maybe** (1) | **Maybe** (1) | **Maybe** (1) | **Maybe** (1) |

| quadratic blowup                       | **Maybe** (1) | **Maybe** (1) | **Maybe** (1) | **Maybe** (1) | **Maybe** (1) |

| external entity expansion (remote)     | False (2)     | False (3)     | False (4)     | False (2)     | false         |

| external entity expansion (local file) | False (2)     | False (3)     | False (4)     | False (2)     | false         |

| DTD retrieval                          | False (2)     | False         | False         | False (2)     | false         |

| gzip bomb                              | False         | False         | False         | False         | **True**      |

| xpath support (6)                      | False         | False         | False         | False         | False         |

| xsl(t) support (6)                     | False         | False         | False         | False         | False         |

| xinclude support (6)                   | False         | **True** (5)  | False         | False         | False         |

| C library                              | expat         | expat         | expat         | expat         | expat         |



vulnerabilities and features



1.  [expat parser](https://libexpat.github.io/) >= 2.4.0 has [billion

    laughs

    protection](https://libexpat.github.io/doc/api/latest/#billion-laughs)

    against XML bombs (CVE-2013-0340). The parser has sensible defaults

    for `XML_SetBillionLaughsAttackProtectionMaximumAmplification` and

    `XML_SetBillionLaughsAttackProtectionActivationThreshold`.

2.  Python >= 3.6.8, >= 3.7.1, and >= 3.8 no longer retrieve local and

    remote resources with urllib, see

    [bpo-17239](https://github.com/python/cpython/issues/61441).

3.  xml.etree doesn't expand entities and raises a ParserError when an

    entity occurs.

4.  minidom doesn't expand entities and simply returns the unexpanded

    entity verbatim.

5.  Library has (limited) XInclude support but requires an additional

    step to process inclusion.

6.  These are features but they may introduce exploitable holes, see

    [Other things to consider](#other-things-to-consider)



### Settings in standard library



#### xml.sax.handler Features



feature_external_ges ()  

disables external entity expansion



feature_external_pes ()  

the option is ignored and doesn't modify any functionality



#### DOM xml.dom.xmlbuilder.Options



external_parameter_entities  

ignored



external_general_entities  

ignored



external_dtd_subset  

ignored



entities  

unsure



## defusedxml



The [defusedxml package](https://github.com/tiran/defusedxml)

([defusedxml on PyPI](https://pypi.python.org/pypi/defusedxml)) contains

several Python-only workarounds and fixes for denial of service and

other vulnerabilities in Python's XML libraries. In order to benefit

from the protection you just have to import and use the listed functions

/ classes from the right defusedxml module instead of the original

module. Merely [defusedxml.xmlrpc](#defusedxml.xmlrpc) is implemented as

monkey patch.



Instead of:



    >>> from xml.etree.ElementTree import parse

    >>> et = parse(xmlfile)



alter code to:



    >>> from defusedxml.ElementTree import parse

    >>> et = parse(xmlfile)









Note






The defusedxml modules are not drop-in replacements of their stdlib

counterparts. The modules only provide functions and classes related to

parsing and loading of XML. For all other features, use the classes,

functions, and constants from the stdlib modules. For example:



    >>> from defusedxml import ElementTree as DET

    >>> from xml.etree.ElementTree as ET



    >>> root = DET.fromstring("")

    >>> root.append(ET.Element("item"))

    >>> ET.tostring(root)

    b''






Additionally the package has an **untested** function to monkey patch

all stdlib modules with `defusedxml.defuse_stdlib()`.









Warning






`defuse_stdlib()` should be avoided. It can break third party package or

cause surprising side effects. Instead you should use the parsing

features of defusedxml explicitly.






All functions and parser classes accept three additional keyword

arguments. They return either the same objects as the original functions

or compatible subclasses.



forbid_dtd (default: False)  

disallow XML with a `` processing instruction and raise a

*DTDForbidden* exception when a DTD processing instruction is found.



forbid_entities (default: True)  

disallow XML with `` declarations inside the DTD and raise an

*EntitiesForbidden* exception when an entity is declared.



forbid_external (default: True)  

disallow any access to remote or local resources in external entities or

DTD and raising an *ExternalReferenceForbidden* exception when a DTD or

entity references an external resource.



### defusedxml (package)



DefusedXmlException, DTDForbidden, EntitiesForbidden,

ExternalReferenceForbidden, NotSupportedError



defuse_stdlib() (*experimental*)



### defusedxml.cElementTree



**NOTE** `defusedxml.cElementTree` is deprecated and will be removed in

a future release. Import from `defusedxml.ElementTree` instead.



parse(), iterparse(), fromstring(), XMLParser



### defusedxml.ElementTree



parse(), iterparse(), fromstring(), XMLParser



### defusedxml.expatreader



create_parser(), DefusedExpatParser



### defusedxml.sax



parse(), parseString(), make_parser()



### defusedxml.expatbuilder



parse(), parseString(), DefusedExpatBuilder, DefusedExpatBuilderNS



### defusedxml.minidom



parse(), parseString()



### defusedxml.pulldom



parse(), parseString()



### defusedxml.xmlrpc



The fix is implemented as monkey patch for the stdlib's xmlrpc package

(3.x) or xmlrpclib module (2.x). The function monkey_patch() enables the fixes, unmonkey_patch() removes the patch and puts the

code in its former state.



The monkey patch protects against XML related attacks as well as

decompression bombs and excessively large requests or responses. The

default setting is 30 MB for requests, responses and gzip decompression.

You can modify the default by changing the module variable MAX_DATA. A value of -1 disables the limit.



### defusedxml.lxml



**DEPRECATED** The module is deprecated and will be removed in a future

release.



lxml is safe against most attack scenarios. lxml uses `libxml2` for

parsing XML. The library has builtin mitigations against billion laughs

and quadratic blowup attacks. The parser allows a limit amount of entity

expansions, then fails. lxml also disables network access by default.

libxml2 [lxml

FAQ](https://lxml.de/FAQ.html#how-do-i-use-lxml-safely-as-a-web-service-endpoint)

lists additional recommendations for safe parsing, for example counter

measures against compression bombs.



The default parser resolves entities and protects against huge trees and

deeply nested entities. To disable entities expansion, use a custom

parser object:



    from lxml import etree



    parser = etree.XMLParser(resolve_entities=False)

    root = etree.fromstring("", parser=parser)



The module acts as an *example* how you could protect code that uses

lxml.etree. It implements a custom Element class that filters out Entity

instances, a custom parser factory and a thread local storage for parser

instances. It also has a check_docinfo() function which inspects a tree

for internal or external DTDs and entity declarations. In order to check

for entities lxml \> 3.0 is required.



parse(), fromstring() RestrictedElement, GlobalParserTLS,

getDefaultParser(), check_docinfo()



## defusedexpat



The [defusedexpat package](https://github.com/tiran/defusedexpat)

([defusedexpat on PyPI](https://pypi.python.org/pypi/defusedexpat)) is

no longer supported. [expat parser](https://libexpat.github.io/) 2.4.0

and newer come with [billion laughs

protection](https://libexpat.github.io/doc/api/latest/#billion-laughs)

against XML bombs.



## How to avoid XML vulnerabilities



Update to Python 3.6.8, 3.7.1, or newer. The SAX and DOM parser do not

load external entities from files or network resources.



Update to expat to 2.4.0 or newer. It has [billion laughs

protection](https://libexpat.github.io/doc/api/latest/#billion-laughs)

with sensible default limits to mitigate billion laughs and quadratic

blowup.



Official binaries from python.org use libexpat 2.4.0 since 3.7.12,

3.8.12, 3.9.7, and 3.10.0 (August 2021). Third party vendors may use

older or newer versions of expat. `pyexpat.version_info` contains the

current runtime version of libexpat. Vendors may have backported fixes

to older versions without bumping the version number.



Example:



    import sys

    import pyexpat



    has_mitigations = (

        sys.version_info >= (3, 7, 1) and

        pyexpat.version_info >= (2, 4, 0)

    )



### Best practices



-   Don't allow DTDs

-   Don't expand entities

-   Don't resolve externals

-   Limit parse depth

-   Limit total input size

-   Limit parse time

-   Favor a SAX or iterparse-like parser for potential large data

-   Validate and properly quote arguments to XSL transformations and

    XPath queries

-   Don't use XPath expression from untrusted sources

-   Don't apply XSL transformations that come untrusted sources



(based on Brad Hill's [Attacking XML

Security](https://www.isecpartners.com/media/12976/iSEC-HILL-Attacking-XML-Security-bh07.pdf))



## Other things to consider



XML, XML parsers and processing libraries have more features and

possible issue that could lead to DoS vulnerabilities or security

exploits in applications. I have compiled an incomplete list of

theoretical issues that need further research and more attention. The

list is deliberately pessimistic and a bit paranoid, too. It contains

things that might go wrong under daffy circumstances.



### attribute blowup / hash collision attack



XML parsers may use an algorithm with quadratic runtime O(n

2) to handle attributes and namespaces. If it uses hash

tables (dictionaries) to store attributes and namespaces the

implementation may be vulnerable to hash collision attacks, thus

reducing the performance to O(n 2) again. In either case an

attacker is able to forge a denial of service attack with an XML

document that contains thousands upon thousands of attributes in a

single node.



I haven't researched yet if expat, pyexpat or libxml2 are vulnerable.



### decompression bomb



The issue of decompression bombs (aka [ZIP

bomb](https://en.wikipedia.org/wiki/Zip_bomb)) apply to all XML

libraries that can parse compressed XML stream like gzipped HTTP streams

or LZMA-ed files. For an attacker it can reduce the amount of

transmitted data by three magnitudes or more. Gzip is able to compress 1

GiB zeros to roughly 1 MB, lzma is even better:



    $ dd if=/dev/zero bs=1M count=1024 | gzip > zeros.gz

    $ dd if=/dev/zero bs=1M count=1024 | lzma -z > zeros.xy

    $ ls -sh zeros.*

    1020K zeros.gz

     148K zeros.xy



None of Python's standard XML libraries decompress streams except for

`xmlrpclib`. The module is vulnerable

\<\> to decompression bombs.



lxml can load and process compressed data through libxml2 transparently.

libxml2 can handle even very large blobs of compressed data efficiently

without using too much memory. But it doesn't protect applications from

decompression bombs. A carefully written SAX or iterparse-like approach

can be safe.



### Processing Instruction



[PI](https://en.wikipedia.org/wiki/Processing_Instruction)'s like:



    



may impose more threats for XML processing. It depends if and how a

processor handles processing instructions. The issue of URL retrieval

with network or local file access apply to processing instructions, too.



### Other DTD features



[DTD](https://en.wikipedia.org/wiki/Document_Type_Definition) has more

features like ``. I haven't researched how these features may

be a security threat.



### XPath



XPath statements may introduce DoS vulnerabilities. Code should never

execute queries from untrusted sources. An attacker may also be able to

create an XML document that makes certain XPath queries costly or

resource hungry.



### XPath injection attacks



XPath injeciton attacks pretty much work like SQL injection attacks.

Arguments to XPath queries must be quoted and validated properly,

especially when they are taken from the user. The page [Avoid the

dangers of XPath

injection](http://www.ibm.com/developerworks/xml/library/x-xpathinjection/index.html)

list some ramifications of XPath injections.



Python's standard library doesn't have XPath support. Lxml supports

parameterized XPath queries which does proper quoting. You just have to

use its xpath() method correctly:



    # DON'T

    >>> tree.xpath("/tag[@id='%s']" % value)



    # instead do

    >>> tree.xpath("/tag[@id=$tagid]", tagid=name)



### XInclude



[XML Inclusion](https://www.w3.org/TR/xinclude/#include_element) is

another way to load and include external files:



    

      

    



This feature should be disabled when XML files from an untrusted source

are processed. Some Python XML libraries and libxml2 support XInclude

but don't have an option to sandbox inclusion and limit it to allowed

directories.



### XMLSchema location



A validating XML parser may download schema files from the information

in a `xsi:schemaLocation` attribute.



    

    



### XSL Transformation



You should keep in mind that XSLT is a Turing complete language. Never

process XSLT code from unknown or untrusted source! XSLT processors may

allow you to interact with external resources in ways you can't even

imagine. Some processors even support extensions that allow read/write

access to file system, access to JRE objects or scripting with Jython.



Example from [Attacking XML

Security](https://www.isecpartners.com/media/12976/iSEC-HILL-Attacking-XML-Security-bh07.pdf)

for Xalan-J:



    

     

       

       

       

       

     

    



## Related CVEs



CVE-2013-1664  

Unrestricted entity expansion induces DoS vulnerabilities in Python XML

libraries (XML bomb)



CVE-2013-1665  

External entity expansion in Python XML libraries inflicts potential

security flaws and DoS vulnerabilities



## Other languages / frameworks



Several other programming languages and frameworks are vulnerable as

well. A couple of them are affected by the fact that libxml2 up to 2.9.0

has no protection against quadratic blowup attacks. Most of them have

potential dangerous default settings for entity expansion and external

entities, too.



### Perl



Perl's XML::Simple is vulnerable to quadratic entity expansion and

external entity expansion (both local and remote).



### Ruby



Ruby's REXML document parser is vulnerable to entity expansion attacks

(both quadratic and exponential) but it doesn't do external entity

expansion by default. In order to counteract entity expansion you have

to disable the feature:



    REXML::Document.entity_expansion_limit = 0



libxml-ruby and hpricot don't expand entities in their default

configuration.



### PHP



PHP's SimpleXML API is vulnerable to quadratic entity expansion and

loads entities from local and remote resources. The option

`LIBXML_NONET` disables network access but still allows local file

access. `LIBXML_NOENT` seems to have no effect on entity expansion in

PHP 5.4.6.



### C# / .NET / Mono



Information in [XML DoS and Defenses

(MSDN)](https://msdn.microsoft.com/en-us/magazine/ee335713.aspx) suggest

that .NET is vulnerable with its default settings. The article contains

code snippets how to create a secure XML reader:



    XmlReaderSettings settings = new XmlReaderSettings();

    settings.ProhibitDtd = false;

    settings.MaxCharactersFromEntities = 1024;

    settings.XmlResolver = null;

    XmlReader reader = XmlReader.Create(stream, settings);



### Java



Untested. The documentation of Xerces and its [Xerces

SecurityMananger](https://xerces.apache.org/xerces2-j/javadocs/xerces2/org/apache/xerces/util/SecurityManager.html)

sounds like Xerces is also vulnerable to billion laugh attacks with its

default settings. It also does entity resolving when an

`org.xml.sax.EntityResolver` is configured. I'm not yet sure about the

default setting here.



Java specialists suggest to have a custom builder factory:



    DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

    builderFactory.setXIncludeAware(False);

    builderFactory.setExpandEntityReferences(False);

    builderFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, True);

    # either

    builderFactory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", True);

    # or if you need DTDs

    builderFactory.setFeature("http://xml.org/sax/features/external-general-entities", False);

    builderFactory.setFeature("http://xml.org/sax/features/external-parameter-entities", False);

    builderFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", False);

    builderFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", False);



## TODO



-   DOM: Use xml.dom.xmlbuilder options for entity handling

-   SAX: take feature_external_ges and feature_external_pes (?) into

    account

-   test experimental monkey patching of stdlib modules

-   improve documentation



## License



Copyright (c) 2013-2023 by Christian Heimes \<\>



Licensed to PSF under a Contributor Agreement.



See  for licensing details.



## Acknowledgements



Brett Cannon (Python Core developer)  

review and code cleanup



Antoine Pitrou (Python Core developer)  

code review



Aaron Patterson, Ben Murphy and Michael Koziarski (Ruby community)  

Many thanks to Aaron, Ben and Michael from the Ruby community for their

report and assistance.



Thierry Carrez (OpenStack)  

Many thanks to Thierry for his report to the Python Security Response

Team on behalf of the OpenStack security team.



Carl Meyer (Django)  

Many thanks to Carl for his report to PSRT on behalf of the Django

security team.



Daniel Veillard (libxml2)  

Many thanks to Daniel for his insight and assistance with libxml2.



semantics GmbH ()  

Many thanks to my employer semantics for letting me work on the issue

during working hours as part of semantics's open source initiative.



## References



-   [XML DoS and Defenses

    (MSDN)](https://msdn.microsoft.com/en-us/magazine/ee335713.aspx)

-   [Billion Laughs](https://en.wikipedia.org/wiki/Billion_laughs) on

    Wikipedia

-   [ZIP bomb](https://en.wikipedia.org/wiki/Zip_bomb) on Wikipedia

-   [Configure SAX parsers for secure

    processing](http://www.ibm.com/developerworks/xml/library/x-tipcfsx/index.html)

-   [Testing for XML

    Injection](https://www.owasp.org/index.php/Testing_for_XML_Injection_(OWASP-DV-008))

# Changelog



## defusedxml 0.8.0



*Release date: 2023*



-   Fix testing without lxml

-   Test on 3.13-dev and PyPy 3.9



## defusedxml 0.8.0rc2



*Release date: 29-Sep-2023*



-   Silence deprecation warning in defuse_stdlib.

-   Update lxml safety information



## defusedxml 0.8.0rc1



*Release date: 26-Sep-2023*



-   Drop support for Python 2.7, 3.4, and 3.5.

-   Test on 3.10, 3.11, and 3.12.

-   Add `defusedxml.ElementTree.fromstringlist()`

-   Update *vulnerabilities and features* table in README.

-   **Pending removal** The `defusedxml.lxml` module has been

    unmaintained and deprecated since 2019. The module will be removed

    in the next version.

-   **Pending removal** The `defusedxml.cElementTree` will be removed in

    the next version. Please use `defusedxml.ElementTree` instead.



## defusedxml 0.7.1



*Release date: 08-Mar-2021*



-   Fix regression `defusedxml.ElementTree.ParseError` (#63) The

    `ParseError` exception is now the same class object as

    `xml.etree.ElementTree.ParseError` again.



## defusedxml 0.7.0



*Release date: 4-Mar-2021*



-   No changes



## defusedxml 0.7.0rc2



*Release date: 12-Jan-2021*



-   Re-add and deprecate `defusedxml.cElementTree`

-   Use GitHub Actions instead of TravisCI

-   Restore `ElementTree` attribute of `xml.etree` module after patching



## defusedxml 0.7.0rc1



*Release date: 04-May-2020*



-   Add support for Python 3.9

-   `defusedxml.cElementTree` is not available with Python 3.9.

-   Python 2 is deprecate. Support for Python 2 will be removed in

    0.8.0.



## defusedxml 0.6.0



*Release date: 17-Apr-2019*



-   Increase test coverage.

-   Add badges to README.



## defusedxml 0.6.0rc1



*Release date: 14-Apr-2019*



-   Test on Python 3.7 stable and 3.8-dev

-   Drop support for Python 3.4

-   No longer pass *html* argument to XMLParse. It has been deprecated

    and ignored for a long time. The DefusedXMLParser still takes a html

    argument. A deprecation warning is issued when the argument is False

    and a TypeError when it's True.

-   defusedxml now fails early when pyexpat stdlib module is not

    available or broken.

-   defusedxml.ElementTree.\_\_all\_\_ now lists ParseError as public

    attribute.

-   The defusedxml.ElementTree and defusedxml.cElementTree modules had a

    typo and used XMLParse instead of XMLParser as an alias for

    DefusedXMLParser. Both the old and fixed name are now available.



## defusedxml 0.5.0



*Release date: 07-Feb-2017*



-   No changes



## defusedxml 0.5.0.rc1



*Release date: 28-Jan-2017*



-   Add compatibility with Python 3.6

-   Drop support for Python 2.6, 3.1, 3.2, 3.3

-   Fix lxml tests (XMLSyntaxError: Detected an entity reference loop)



## defusedxml 0.4.1



*Release date: 28-Mar-2013*



-   Add more demo exploits, e.g. python_external.py and Xalan XSLT

    demos.

-   Improved documentation.



## defusedxml 0.4



*Release date: 25-Feb-2013*



-   As per  please REJECT

    CVE-2013-0278, CVE-2013-0279 and CVE-2013-0280 and use

    CVE-2013-1664, CVE-2013-1665 for OpenStack/etc.

-   Add missing parser_list argument to sax.make_parser(). The argument

    is ignored, though. (thanks to Florian Apolloner)

-   Add demo exploit for external entity attack on Python's SAX parser,

    XML-RPC and WebDAV.



## defusedxml 0.3



*Release date: 19-Feb-2013*



-   Improve documentation



## defusedxml 0.2



*Release date: 15-Feb-2013*



-   Rename ExternalEntitiesForbidden to ExternalReferenceForbidden

-   Rename defusedxml.lxml.check_dtd() to check_docinfo()

-   Unify argument names in callbacks

-   Add arguments and formatted representation to exceptions

-   Add forbid_external argument to all functions and classes

-   More tests

-   LOTS of documentation

-   Add example code for other languages (Ruby, Perl, PHP) and parsers

    (Genshi)

-   Add protection against XML and gzip attacks to xmlrpclib



## defusedxml 0.1



*Release date: 08-Feb-2013*



-   Initial and internal release for PSRT review