Just out of curiosity, is there an allowed way to access directories like this? Sudo doesn't let me see the contents of the ~/Library/Safari directory. Can non-Apple programs access this, like backup programs? Can I bless a script to access this? Can Mozilla or others import bookmarks from Safari any more?
The report shows that given a path, any app can access file metadata or learn that no such file exists outside the sandbox. It does not show access to file data itself. The Safari specific part of the report is data leak caused by the fact that Safari embeds sensitive information (URLs) into file metadata (name).
I believe you can access those directories by either enabling Full Disk Access for the process of interest or by disabling System Integrity Protection.
