HTML Purifier 3.1.1 is a security and bugfix release. This release addresses
two security vulnerabilities, both related to CSS, and one of which only
applies to users using Shift_JIS as their output encoding. There is also
a security improvement regarding the imagecrash attack. There is a backwards
incompatible change in which resources are no longer munged
by default; please enable using %URI.MungeResources. Besides this, there
are numerous improvements to URI munging, esp. with the addition of
%URI.MungeSecretKey, as well as an experimental %HTML.SafeObject and %HTML.SafeEmbed.