Variable: untrusted-content
untrusted-content is a buffer-local variable defined in files.el.gz.
Documentation
Non-nil means that current buffer originated from an untrusted source.
Email clients and some other modes may set this non-nil to mark the buffer contents as untrusted.
This variable might be subject to change without notice.
Probably introduced at or before Emacs version 29.3.
Source Code
;; Defined in /usr/src/emacs/lisp/files.el.gz
(defvar-local untrusted-content nil
"Non-nil means that current buffer originated from an untrusted source.
Email clients and some other modes may set this non-nil to mark the
buffer contents as untrusted.
This variable might be subject to change without notice.")