Issue #15445: Updated logging configuration documentation to highlight potential…

Issue #15445: Updated logging configuration documentation to highlight potential security risk posed by listen() in certain scenarios.

Doc/library/logging.config.rst

@@ -109,6 +109,19 @@ in :mod:`logging` itself) and defining handlers which are declared either in
    send it to the socket as a string of bytes preceded by a four-byte length
    string packed in binary using ``struct.pack('>L', n)``.
 
+   .. note:: Because portions of the configuration are passed through
+      :func:`eval`, use of this function may open its users to a security risk.
+      While the function only binds to a socket on ``localhost``, and so does
+      not accept connections from remote machines, there are scenarios where
+      untrusted code could be run under the account of the process which calls
+      :func:`listen`. Specifically, if the process calling :func:`listen` runs
+      on a multi-user machine where users cannot trust each other, then a
+      malicious user could arrange to run essentially arbitrary code in a
+      victim user's process, simply by connecting to the victim's
+      :func:`listen` socket and sending a configuration which runs whatever
+      code the attacker wants to have executed in the victim's process. This is
+      especially easy to do if the default port is used, but not hard even if a
+      different port is used).
 
 .. function:: stopListening()
 
@@ -694,6 +707,12 @@ The ``class`` entry is optional.  It indicates the name of the formatter's class
 :class:`Formatter` subclass.  Subclasses of :class:`Formatter` can present
 exception tracebacks in an expanded or condensed format.
 
+.. note:: Due to the use of :func:`eval` as described above, there are
+   potential security risks which result from using the :func:`listen` to send
+   and receive configurations via sockets. The risks are limited to where
+   multiple users with no mutual trust run code on the same machine; see the
+   :func:`listen` documentation for more information.
+
 .. seealso::
 
    Module :mod:`logging`