pg_upgrade normally restricts its temporary files to be readable and writable only by the calling user. But the temporary file containing pg_dum
pall -g output would be group- or world-readable, or even writable, if the user's umask setting allows. In typical usage on multi-user machines, the umask an
d/or the working directory's permissions would be tight enough to prevent problems; but there may be people using pg_upgrade in scenarios where this oversigh
t would permit disclosure of database passwords to unfriendly eyes.