From the NEWS file: Emacs 29.3 is an emergency bugfix release intended to fix several security vulnerabilities described below.

• Arbitrary Lisp code is no longer evaluated as part of turning on Org mode. This is for security reasons, to avoid evaluating malicious Lisp code.

• New buffer-local variable ‘untrusted-content’. When this is non-nil, Lisp programs should treat buffer contents with extra caution.

• Gnus now treats inline MIME contents as untrusted. To get back previous insecure behavior, ‘untrusted-content’ should be reset to nil in the buffer.

• LaTeX preview is now by default disabled for email attachments. To get back previous insecure behavior, set the variable ‘org–latex-preview-when-risky’ to a non-nil value.

• Org mode now considers contents of remote files to be untrusted. Remote files are recognized by calling ‘file-remote-p’.