I wasn't concerned so much with security, but with user experience.
For instance, some editors don't perform fsync-then-rename, but simply
truncate the file when saving (because they want to preserve hard
links). With XFS, this tends to cause null bytes on crashes. Since
ext3 has got a much larger install base, this would result in lots of
bug reports, I fear.
Without zeroing, the truncating editor might garble the file in a more
obvious way, but you've got the security issue (and I agree that this
is more of a PR issue).
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