The serializer in html5lib before 0.99999999 might allow remote attackers to conduct cross-site scripting (XSS) attacks by leveraging mishandling of the < (less than) character in attribute values.
References
- https://nvd.nist.gov/vuln/detail/CVE-2016-9909
- https://github.com/html5lib/html5lib-python/issues/11
- https://github.com/html5lib/html5lib-python/issues/12
- https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7
- https://html5lib.readthedocs.io/en/latest/changes.html#b9
- http://www.openwall.com/lists/oss-security/2016/12/06/5
- http://www.openwall.com/lists/oss-security/2016/12/08/8
- https://github.com/advisories/GHSA-v9v9-xffq-rwr4