Comment 1 for bug 457791

We are already using SQLITE_SECURE_DELETE (see bug 405925). Maybe you're confusing the history data (that is cleared with Tools > Clear Private Data) with the bookmark data, which is stored in the same database.

Note that VACUUM only shrinks the file, but doesn't really help your privacy, because the old data can still be found on your hard disk (although much more difficult to recover). We're not doing a VACUUM right now, since it's very slow. But there's lots of bugs open about it, mainly to shrink the databases.