This has come up often enough now on the tracker that it deserves a FAQ entry.

Based on report and patch by Aaron Oakley.

Issue #17980: Fix possible abuse of ssl.match_hostname() for denial of service using certificates with many wildcards (CVE-2013-2099).

This caused an exception to be raised later than expected.

Use the cleaner looking @property style for __dict__.
Move _replace() to be just after make() to indicate that
it is a core method on named tuples.

to the new section.

  in urllib.request.urlopen() is fixed to match the code.

characters() and ignorableWhitespace() methods.  Original patch by Sebastian
Ortiz Vasquez.