XML Parsing Vulnerability affecting JRuby users

The ActiveSupport XML parsing functionality supports multiple
pluggable backends. One backend supported for JRuby users is
ActiveSupport::XmlMini_JDOM which makes use of the
javax.xml.parsers.DocumentBuilder class. In some JVM configurations
the default settings of that class can allow an attacker to construct
XML which, when parsed, will contain the contents of arbitrary URLs
including files from the application server. They may also allow for
various denial of service attacks. Action Pack