Document the change in a NEWS entry of the Security category.
extsep = '.'
sep = '/'
pathsep = ':'
-defpath = ':/bin:/usr/bin'
+defpath = '/bin:/usr/bin'
altsep = None
devnull = '/dev/null'
--- /dev/null
+:func:`shutil.which` now uses ``os.confstr("CS_PATH")`` if available and if the
+:envvar:`PATH` environment variable is not set. Remove also the current
+directory from :data:`posixpath.defpath`. On Unix, :func:`shutil.which` and the
+:mod:`subprocess` module no longer search the executable in the current
+directory if the :envvar:`PATH` environment variable is not set.