DeltaSync — KeePass search & go collects no data. There is no analytics, no
telemetry, no remote code, and no server of any kind involved in what this
add-on does.

WHAT IT HANDLES
To let you search, the add-on holds a list of entry titles, web addresses and
group names from your own KeePass database. That list is produced on your own
computer by the DeltaSync native application, which you install yourself, and
it reaches the add-on over a local channel that never leaves your machine.

WHAT IT NEVER SEES
Passwords, usernames, notes, attachments and custom fields are never sent to
the add-on. The native application enforces this on its side: it can only
serialise an entry's identifier, title, web addresses and group path, so no
change to this add-on could cause anything else to be exposed. Your master
password is read by the native application from your operating system's
credential store and never passes through Firefox.

WHERE IT IS KEPT
The search list is held in session storage, which lives in memory only. It is
discarded when you close Firefox, and the Lock button in the add-on clears it
immediately. Nothing is written to disk by the add-on.

The full source code and the design behind these boundaries are public:
https://gitlab.com/Star95/keepass-deltasync