cpython/Misc/NEWS.d/next/Library/2022-11-10-17-16-45.gh-issue-97514.kzA0zl.rst

Authentication was added to the :mod:`multiprocessing` forkserver start
method control socket so that only processes with the authentication key
generated by the process that spawned the forkserver can control it.  This
is an enhancement over the other :gh:`97514` fixes so that access is no
longer limited only by filesystem permissions.

The file descriptor exchange of control pipes with the forked worker process
now requires an explicit acknowledgement byte to be sent over the socket after
the exchange on all forkserver supporting platforms. That makes testing the
above much easier.