The Emacs command `run-python' launches an interactive
Python interpreter. After the Python process starts up,
Emacs automatically sends it the line:
import emacs
which normally imports a script named emacs.py which is
distributed with Emacs. This script, which is typically
located in a write-protected installation directory with
other Emacs program files, defines various functions to help
the Python process communicate with Emacs.
The vulnerability arises because Python, by default,
prepends '' to the module search path, so modules are looked
for in the current directory. If the current directory is
world-writable, an attacker may insert malicious code by
adding a fake Python module named emacs.py into that
directory.