Soul s2: under a permissive umask the store was group/world-writable between
CultCache's rename and the chmod, and an fd opened there survived it. The
mind-control binary now sets umask 077 first (the library never touches the
umask). The writer refuses to write through an existing directory, lock or store
that is not root's or is group/world-writable, with the typed UnsafeStore error
naming path, mode and owner. Tests: a non-root open-for-write probe against the
real binary under umask 000; refusals for 0777/0775 directories, 0666/0664
locks and stores, and a non-root-owned directory; accepted root installs.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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