In elisp-mode.el in GNU Emacs through 30.0.92, a user who chooses to invoke elisp-completion-at-point (for code completion) on untrusted Emacs Lisp source code can trigger unsafe Lisp macro expansion that allows attackers to execute arbitrary code. (This unsafe expansion also occurs if a user chooses to enable on-the-fly diagnosis that byte compiles untrusted Emacs Lisp source code.)

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-53920
• https://eshelyaron.com/posts/2024-11-27-emacs-aritrary-code-execution-and-how-to-avoid-it.html
• https://git.savannah.gnu.org/cgit/emacs.git/tag/?h=emacs-30.0.92
• https://git.savannah.gnu.org/cgit/emacs.git/tree/ChangeLog.4
• https://yhetil.org/emacs/CAFXAjY5f4YfHAtZur1RAqH34UbYU56_t6t2Er0YEh1Sb7-W=hg%40mail.gmail.com
• https://news.ycombinator.com/item?id=42256409