An easy safelist-based HTML-sanitizing tool.
Project description
NOTE: 2023-01-23: Bleach is deprecated. See issue: https://github.com/mozilla/bleach/issues/698
Bleach is an allowed-list-based HTML sanitizing library that escapes or strips markup and attributes.
Bleach can also linkify text safely, applying filters that Django’s urlize filter cannot, and optionally setting rel attributes, even on links already in the text.
Bleach is intended for sanitizing text from untrusted sources. If you find yourself jumping through hoops to allow your site administrators to do lots of things, you’re probably outside the use cases. Either trust those users, or don’t.
Because it relies on html5lib, Bleach is as good as modern browsers at dealing with weird, quirky HTML fragments. And any of Bleach’s methods will fix unbalanced or mis-nested tags.
The version on GitHub is the most up-to-date and contains the latest bug fixes. You can find full documentation on ReadTheDocs.
- Code:
- Documentation:
- Issue tracker:
- License:
Apache License v2; see LICENSE file
Reporting Bugs
For regular bugs, please report them in our issue tracker.
If you believe that you’ve found a security vulnerability, please file a secure bug report in our bug tracker or send an email to security AT mozilla DOT org.
For more information on security-related bug disclosure and the PGP key to use for sending encrypted mail or to verify responses received from that address, please read our wiki page at https://www.mozilla.org/en-US/security/#For_Developers.
Security
Bleach is a security-focused library.
We have a responsible security vulnerability reporting process. Please use that if you’re reporting a security issue.
Security issues are fixed in private. After we land such a fix, we’ll do a release.
For every release, we mark security issues we’ve fixed in the CHANGES in the Security issues section. We include any relevant CVE links.
Installing Bleach
Bleach is available on PyPI, so you can install it with pip:
$ pip install bleach
Upgrading Bleach
Basic use
The simplest way to use Bleach is:
>>> import bleach
>>> bleach.clean('an <script>evil()</script> example')
u'an <script>evil()</script> example'
>>> bleach.linkify('an http://example.com url')
u'an <a href="http://example.com" rel="nofollow">http://example.com</a> url'Code of Conduct
This project and repository is governed by Mozilla’s code of conduct and etiquette guidelines. For more details please see the CODE_OF_CONDUCT.md
Bleach changes
Version 6.2.0 (October 29th, 2024)
Backwards incompatible changes
Dropped support for Python 3.8. (#737)
Security fixes
None
Bug fixes
Add support for Python 3.13. (#736)
Remove six depdenncy. (#618)
Update known-good versions for tinycss2. (#732)
Fix additional < followed by characters and EOF issues. (#728)
Version 6.1.0 (October 6th, 2023)
Backwards incompatible changes
Dropped support for Python 3.7. (#709)
Security fixes
None
Bug fixes
Add support for Python 3.12. (#710)
Fix linkify with arrays in querystring (#436)
Handle more cases with < followed by character data (#705)
Fix entities inside a tags in linkification (#704)
Update cap for tinycss2 to <1.3 (#702)
Updated Sphinx requirement
Add dependabot for github actions and update github actions
Version 6.0.0 (January 23rd, 2023)
Backwards incompatible changes
bleach.clean, bleach.sanitizer.Cleaner, bleach.html5lib_shim.BleachHTMLParser: the tags and protocols arguments were changed from lists to sets.
Old pre-6.0.0:
bleach.clean( "some text", tags=["a", "p", "img"], # ^ ^ list protocols=["http", "https"], # ^ ^ list )New 6.0.0 and later:
bleach.clean( "some text", tags={"a", "p", "img"}, # ^ ^ set protocols={"http", "https"}, # ^ ^ set )bleach.linkify, bleach.linkifier.Linker: the skip_tags and recognized_tags arguments were changed from lists to sets.
Old pre-6.0.0:
bleach.linkify( "some text", skip_tags=["pre"], # ^ ^ list ) linker = Linker( skip_tags=["pre"], # ^ ^ list recognized_tags=html5lib_shim.HTML_TAGS + ["custom-element"], # ^ ^ ^ list # | # | list concatenation )New 6.0.0 and later:
bleach.linkify( "some text", skip_tags={"pre"}, # ^ ^ set ) linker = Linker( skip_tags={"pre"}, # ^ ^ set recognized_tags=html5lib_shim.HTML_TAGS | {"custom-element"}, # ^ ^ ^ set # | # | union operator )bleach.sanitizer.BleachSanitizerFilter: strip_allowed_elements is now strip_allowed_tags. We now use “tags” everywhere rather than a mishmash of “tags” in some places and “elements” in others.
Security fixes
None
Bug fixes
Add support for Python 3.11. (#675)
Fix API weirness in BleachSanitizerFilter. (#649)
We’re using “tags” instead of “elements” everywhere–no more weird overloading of “elements” anymore.
Also, it no longer calls the superclass constructor.
Add warning when css_sanitizer isn’t set, but the style attribute is allowed. (#676)
Fix linkify handling of character entities. (#501)
Rework dev dependencies to use requirements-dev.txt and requirements-flake8.txt instead of extras.
Fix project infrastructure to be tox-based so it’s easier to have CI run the same things we’re running in development and with flake8 in an isolated environment.
Update action versions in CI.
Switch to f-strings where possible. Make tests parametrized to be easier to read/maintain.
Version 5.0.1 (June 27th, 2022)
Security fixes
None
Bug fixes
Add missing comma to tinycss2 require. Thank you, @shadchin!
Add url parse tests based on wpt url tests. (#688)
Support scheme-less urls if “https” is in allow list. (#662)
Handle escaping < in edge cases where it doesn’t start a tag. (#544)
Fix reference warnings in docs. (#660)
Correctly urlencode email address parts. Thank you, @larseggert! (#659)
Version 5.0.0 (April 7th, 2022)
Backwards incompatible changes
clean and linkify now preserve the order of HTML attributes. Thank you, @askoretskly! (#566)
Drop support for Python 3.6. Thank you, @hugovk! (#629)
CSS sanitization in style tags is completely different now. If you’re using Bleach clean to sanitize css in style tags, you’ll need to update your code and you’ll need to install the css extras:
pip install 'bleach[css]'
See the documentation on sanitizing CSS for how to do it. (#633)
Security fixes
None
Bug fixes
Rework dev dependencies. We no longer have requirements-dev.in/requirements-dev.txt. Instead, we’re using dev extras.
See development docs for more details. (#620)
Add newline when dropping block-level tags. Thank you, @jvanasco! (#369)
Version 4.1.0 (August 25th, 2021)
Features
Python 3.9 support
Security fixes
None
Bug fixes
Update sanitizer clean to use vendored 3.6.14 stdlib urllib.parse to fix test failures on Python 3.9. (#536)
Version 4.0.0 (August 3rd, 2021)
Backwards incompatible changes
Drop support for unsupported Python versions <3.6. (#520)
Security fixes
None
Features
fix attribute name in the linkify docs (thanks @CheesyFeet!)
Version 3.3.1 (July 14th, 2021)
Security fixes
None
Features
add more tests for CVE-2021-23980 / GHSA-vv2x-vrpj-qqpq
bump python version to 3.8 for tox doc, vendorverify, and lint targets
update bug report template tag
update vendorverify script to detect and fail when extra files are vendored
update release process docs to check vendorverify passes locally
Bug fixes
remove extra vendored django present in the v3.3.0 whl (#595)
duplicate h1 header doc fix (thanks Nguyễn Gia Phong / @McSinyx!)
Version 3.3.0 (February 1st, 2021)
Backwards incompatible changes
clean escapes HTML comments even when strip_comments=False
Security fixes
Fix bug 1621692 / GHSA-m6xf-fq7q-8743. See the advisory for details.
Features
None
Bug fixes
None
Version 3.2.3 (January 26th, 2021)
Security fixes
None
Features
None
Bug fixes
fix clean and linkify raising ValueErrors for certain inputs. Thank you @Google-Autofuzz.
Version 3.2.2 (January 20th, 2021)
Security fixes
None
Features
Migrate CI to Github Actions. Thank you @hugovk.
Bug fixes
fix linkify raising an IndexError on certain inputs. Thank you @Google-Autofuzz.
Version 3.2.1 (September 18th, 2020)
Security fixes
None
Features
None
Bug fixes
change linkifier to add rel=”nofollow” as documented. Thank you @mitar.
suppress html5lib sanitizer DeprecationWarnings (#557)
Version 3.2.0 (September 16th, 2020)
Security fixes
None
Features
None
Bug fixes
html5lib dependency to version 1.1.0. Thank you Sam Sneddon.
update tests_website terminology. Thank you Thomas Grainger.
Version 3.1.5 (April 29th, 2020)
Security fixes
None
Features
None
Bug fixes
replace missing setuptools dependency with packaging. Thank you Benjamin Peterson.
Version 3.1.4 (March 24th, 2020)
Security fixes
bleach.clean behavior parsing style attributes could result in a regular expression denial of service (ReDoS).
Calls to bleach.clean with an allowed tag with an allowed style attribute were vulnerable to ReDoS. For example, bleach.clean(..., attributes={'a': ['style']}).
This issue was confirmed in Bleach versions v3.1.3, v3.1.2, v3.1.1, v3.1.0, v3.0.0, v2.1.4, and v2.1.3. Earlier versions used a similar regular expression and should be considered vulnerable too.
Anyone using Bleach <=v3.1.3 is encouraged to upgrade.
Backwards incompatible changes
Style attributes with dashes, or single or double quoted values are cleaned instead of passed through.
Features
None
Bug fixes
None
Version 3.1.3 (March 17th, 2020)
Security fixes
None
Backwards incompatible changes
Drop support for Python 3.4. Thank you, @hugovk!
Drop deprecated setup.py test support. Thank you, @jdufresne! (#507)
Features
Add support for Python 3.8. Thank you, @jdufresne!
Add support for PyPy 7. Thank you, @hugovk!
Add pypy3 testing to tox and travis. Thank you, @jdufresne!
Bug fixes
Add relative link to code of conduct. (#442)
Fix typo: curren -> current in tests/test_clean.py Thank you, timgates42! (#504)
Fix handling of non-ascii style attributes. Thank you, @sekineh! (#426)
Simplify tox configuration. Thank you, @jdufresne!
Make documentation reproducible. Thank you, @lamby!
Fix typos in code comments. Thank you, @zborboa-g!
Fix exception value testing. Thank you, @mastizada!
Fix parser-tags NoneType exception. Thank you, @bope!
Improve TLD support in linkify. Thank you, @pc-coholic!
Version 3.1.2 (March 11th, 2020)
Security fixes
bleach.clean behavior parsing embedded MathML and SVG content with RCDATA tags did not match browser behavior and could result in a mutation XSS.
Calls to bleach.clean with strip=False and math or svg tags and one or more of the RCDATA tags script, noscript, style, noframes, iframe, noembed, or xmp in the allowed tags whitelist were vulnerable to a mutation XSS.
This security issue was confirmed in Bleach version v3.1.1. Earlier versions are likely affected too.
Anyone using Bleach <=v3.1.1 is encouraged to upgrade.
Backwards incompatible changes
None
Features
None
Bug fixes
None
Version 3.1.1 (February 13th, 2020)
Security fixes
bleach.clean behavior parsing noscript tags did not match browser behavior.
Calls to bleach.clean allowing noscript and one or more of the raw text tags (title, textarea, script, style, noembed, noframes, iframe, and xmp) were vulnerable to a mutation XSS.
This security issue was confirmed in Bleach versions v2.1.4, v3.0.2, and v3.1.0. Earlier versions are probably affected too.
Anyone using Bleach <=v3.1.0 is highly encouraged to upgrade.
Backwards incompatible changes
None
Features
None
Bug fixes
None
Version 3.1.0 (January 9th, 2019)
Security fixes
None
Backwards incompatible changes
None
Features
Add recognized_tags argument to the linkify Linker class. This fixes issues when linkifying on its own and having some tags get escaped. It defaults to a list of HTML5 tags. Thank you, Chad Birch! (#409)
Bug fixes
Add six>=1.9 to requirements. Thank you, Dave Shawley (#416)
Fix cases where attribute names could have invalid characters in them. (#419)
Fix problems with LinkifyFilter not being able to match links across &. (#422)
Fix InputStreamWithMemory when the BleachHTMLParser is parsing meta tags. (#431)
Fix doctests. (#357)
Version 3.0.2 (October 11th, 2018)
Security fixes
None
Backwards incompatible changes
None
Features
None
Bug fixes
Merge Characters tokens after sanitizing them. This fixes issues in the LinkifyFilter where it was only linkifying parts of urls. (#374)
Version 3.0.1 (October 9th, 2018)
Security fixes
None
Backwards incompatible changes
None
Features
Support Python 3.7. It supported Python 3.7 just fine, but we added 3.7 to the list of Python environments we test so this is now officially supported. (#377)
Bug fixes
Fix list object has no attribute lower in clean. (#398)
Fix abbr getting escaped in linkify. (#400)
Version 3.0.0 (October 3rd, 2018)
Security fixes
None
Backwards incompatible changes
A bunch of functions were moved from one module to another.
These were moved from bleach.sanitizer to bleach.html5lib_shim:
convert_entity
convert_entities
match_entity
next_possible_entity
BleachHTMLSerializer
BleachHTMLTokenizer
BleachHTMLParser
These functions and classes weren’t documented and aren’t part of the public API, but people read code and might be using them so we’re considering it an incompatible API change.
If you’re using them, you’ll need to update your code.
Features
Bleach no longer depends on html5lib. html5lib==1.0.1 is now vendored into Bleach. You can remove it from your requirements file if none of your other requirements require html5lib.
This means Bleach will now work fine with other libraries that depend on html5lib regardless of what version of html5lib they require. (#386)
Bug fixes
Fixed tags getting added when using clean or linkify. This was a long-standing regression from the Bleach 2.0 rewrite. (#280, #392)
Fixed <isindex> getting replaced with a string. Now it gets escaped or stripped depending on whether it’s in the allowed tags or not. (#279)
Version 2.1.4 (August 16th, 2018)
Security fixes
None
Backwards incompatible changes
Dropped support for Python 3.3. (#328)
Features
None
Bug fixes
Handle ambiguous ampersands in correctly. (#359)
Version 2.1.3 (March 5th, 2018)
Security fixes
Attributes that have URI values weren’t properly sanitized if the values contained character entities. Using character entities, it was possible to construct a URI value with a scheme that was not allowed that would slide through unsanitized.
This security issue was introduced in Bleach 2.1. Anyone using Bleach 2.1 is highly encouraged to upgrade.
Backwards incompatible changes
None
Features
None
Bug fixes
Fixed some other edge cases for attribute URI value sanitizing and improved testing of this code.
Version 2.1.2 (December 7th, 2017)
Security fixes
None
Backwards incompatible changes
None
Features
None
Bug fixes
Support html5lib-python 1.0.1. (#337)
Add deprecation warning for supporting html5lib-python < 1.0.
Switch to semver.
Version 2.1.1 (October 2nd, 2017)
Security fixes
None
Backwards incompatible changes
None
Features
None
Bug fixes
Fix setup.py opening files when LANG=. (#324)
Version 2.1 (September 28th, 2017)
Security fixes
Convert control characters (backspace particularly) to “?” preventing malicious copy-and-paste situations. (#298)
See https://github.com/mozilla/bleach/issues/298 for more details.
This affects all previous versions of Bleach. Check the comments on that issue for ways to alleviate the issue if you can’t upgrade to Bleach 2.1.
Backwards incompatible changes
Redid versioning. bleach.VERSION is no longer available. Use the string version at bleach.__version__ and parse it with pkg_resources.parse_version. (#307)
clean, linkify: linkify and clean should only accept text types; thank you, Janusz! (#292)
clean, linkify: accept only unicode or utf-8-encoded str (#176)
Features
Bug fixes
bleach.clean() no longer unescapes entities including ones that are missing a ; at the end which can happen in urls and other places. (#143)
linkify: fix http links inside of mailto links; thank you, sedrubal! (#300)
clarify security policy in docs (#303)
fix dependency specification for html5lib 1.0b8, 1.0b9, and 1.0b10; thank you, Zoltán! (#268)
add Bleach vs. html5lib comparison to README; thank you, Stu Cox! (#278)
fix KeyError exceptions on tags without href attr; thank you, Alex Defsen! (#273)
add test website and scripts to test bleach.clean() output in browser; thank you, Greg Guthe!
Version 2.0 (March 8th, 2017)
Security fixes
None
Backwards incompatible changes
Removed support for Python 2.6. (#206)
Removed support for Python 3.2. (#224)
Bleach no longer supports html5lib < 0.99999999 (8 9s).
This version is a rewrite to use the new sanitizing API since the old one was dropped in html5lib 0.99999999 (8 9s).
If you’re using 0.9999999 (7 9s) upgrade to 0.99999999 (8 9s) or higher.
If you’re using 1.0b8 (equivalent to 0.9999999 (7 9s)), upgrade to 1.0b9 (equivalent to 0.99999999 (8 9s)) or higher.
bleach.clean and friends were rewritten
clean was reimplemented as an html5lib filter and happens at a different step in the HTML parsing -> traversing -> serializing process. Because of that, there are some differences in clean’s output as compared with previous versions.
Amongst other things, this version will add end tags even if the tag in question is to be escaped.
bleach.clean and friends attribute callables now take three arguments: tag, attribute name and attribute value. Previously they only took attribute name and attribute value.
All attribute callables will need to be updated.
bleach.linkify was rewritten
linkify was reimplemented as an html5lib Filter. As such, it no longer accepts a tokenizer argument.
The callback functions for adjusting link attributes now takes a namespaced attribute.
Previously you’d do something like this:
def check_protocol(attrs, is_new): if not attrs.get('href', '').startswith('http:', 'https:')): return None return attrsNow it’s more like this:
def check_protocol(attrs, is_new): if not attrs.get((None, u'href'), u'').startswith(('http:', 'https:')): # ^^^^^^^^^^^^^^^ return None return attrsFurther, you need to make sure you’re always using unicode values. If you don’t then html5lib will raise an assertion error that the value is not unicode.
All linkify filters will need to be updated.
bleach.linkify and friends had a skip_pre argument–that’s been replaced with a more general skip_tags argument.
Before, you might do:
bleach.linkify(some_text, skip_pre=True)
The equivalent with Bleach 2.0 is:
bleach.linkify(some_text, skip_tags=['pre'])
You can skip other tags, too, like style or script or other places where you don’t want linkification happening.
All uses of linkify that use skip_pre will need to be updated.
Changes
Supports Python 3.6.
Supports html5lib >= 0.99999999 (8 9s).
There’s a bleach.sanitizer.Cleaner class that you can instantiate with your favorite clean settings for easy reuse.
There’s a bleach.linkifier.Linker class that you can instantiate with your favorite linkify settings for easy reuse.
There’s a bleach.linkifier.LinkifyFilter which is an htm5lib filter that you can pass as a filter to bleach.sanitizer.Cleaner allowing you to clean and linkify in one pass.
bleach.clean and friends can now take a callable as an attributes arg value.
Tons of bug fixes.
Cleaned up tests.
Documentation fixes.
Version 1.5 (November 4th, 2016)
Security fixes
None
Backwards incompatible changes
clean: The list of ALLOWED_PROTOCOLS now defaults to http, https and mailto.
Previously it was a long list of protocols something like ed2k, ftp, http, https, irc, mailto, news, gopher, nntp, telnet, webcal, xmpp, callto, feed, urn, aim, rsync, tag, ssh, sftp, rtsp, afs, data. (#149)
Changes
clean: Added protocols to arguments list to let you override the list of allowed protocols. Thank you, Andreas Malecki! (#149)
linkify: Fix a bug involving periods at the end of an email address. Thank you, Lorenz Schori! (#219)
linkify: Fix linkification of non-ascii ports. Thank you Alexandre, Macabies! (#207)
linkify: Fix linkify inappropriately removing node tails when dropping nodes. (#132)
Fixed a test that failed periodically. (#161)
Switched from nose to py.test. (#204)
Add test matrix for all supported Python and html5lib versions. (#230)
Limit to html5lib >=0.999,!=0.9999,!=0.99999,<0.99999999 because 0.9999 and 0.99999 are busted.
Add support for python setup.py test. (#97)
Version 1.4.3 (May 23rd, 2016)
Security fixes
None
Changes
Limit to html5lib >=0.999,<0.99999999 because of impending change to sanitizer api. #195
Version 1.4.2 (September 11, 2015)
Changes
linkify: Fix hang in linkify with parse_email=True. (#124)
linkify: Fix crash in linkify when removing a link that is a first-child. (#136)
Updated TLDs.
linkify: Don’t remove exterior brackets when linkifying. (#146)
Version 1.4.1 (December 15, 2014)
Changes
Consistent order of attributes in output.
Python 3.4 support.
Version 1.4 (January 12, 2014)
Changes
linkify: Update linkify to use etree type Treewalker instead of simpletree.
Updated html5lib to version >=0.999.
Update all code to be compatible with Python 3 and 2 using six.
Switch to Apache License.
Version 1.3
Used by Python 3-only fork.
Version 1.2.2 (May 18, 2013)
Pin html5lib to version 0.95 for now due to major API break.
Version 1.2.1 (February 19, 2013)
clean() no longer considers feed: an acceptable protocol due to inconsistencies in browser behavior.
Version 1.2 (January 28, 2013)
linkify() has changed considerably. Many keyword arguments have been replaced with a single callbacks list. Please see the documentation for more information.
Bleach will no longer consider unacceptable protocols when linkifying.
linkify() now takes a tokenizer argument that allows it to skip sanitization.
delinkify() is gone.
Removed exception handling from _render. clean() and linkify() may now throw.
linkify() correctly ignores case for protocols and domain names.
linkify() correctly handles markup within an <a> tag.
Version 1.1.5
Version 1.1.4
Version 1.1.3 (July 10, 2012)
Fix parsing bare URLs when parse_email=True.
Version 1.1.2 (June 1, 2012)
Fix hang in style attribute sanitizer. (#61)
Allow / in style attribute values.
Version 1.1.1 (February 17, 2012)
Fix tokenizer for html5lib 0.9.5.
Version 1.1.0 (October 24, 2011)
linkify() now understands port numbers. (#38)
Documented character encoding behavior. (#41)
Add an optional target argument to linkify().
Add delinkify() method. (#45)
Support subdomain whitelist for delinkify(). (#47, #48)
Version 1.0.4 (September 2, 2011)
Switch to SemVer git tags.
Make linkify() smarter about trailing punctuation. (#30)
Pass exc_info to logger during rendering issues.
Add wildcard key for attributes. (#19)
Make linkify() use the HTMLSanitizer tokenizer. (#36)
Fix URLs wrapped in parentheses. (#23)
Make linkify() UTF-8 safe. (#33)
Version 1.0.3 (June 14, 2011)
linkify() works with 3rd level domains. (#24)
clean() supports vendor prefixes in style values. (#31, #32)
Fix linkify() email escaping.
Version 1.0.2 (June 6, 2011)
linkify() supports email addresses.
clean() supports callables in attributes filter.
Version 1.0.1 (April 12, 2011)
linkify() doesn’t drop trailing slashes. (#21)
linkify() won’t linkify ‘libgl.so.1’. (#22)
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