PUT /api/v1/admin/settings is a whole-document write. The admin UI always sends
the complete document, so saving from the settings page is unaffected both
before and after this change. The bug is only reachable when an API client calls
the endpoint directly and sends just the fields it wants to change, which is the
natural assumption for a PUT on a settings resource.
Value-typed fields of UpdateSettingsRequest bind to their zero value when the
payload omits them, and buildSystemSettingsUpdates writes every key
unconditionally, so such a caller has no way to say "leave this one alone".
Omitting a field and explicitly clearing it are indistinguishable on the wire.
A caller that sends only the field it wants to change, e.g.
{"risk_control_enabled": true}
sets that flag and clears every other unguarded field in the same request.
Measured against a fully configured store, one such call empties site_name,
site_subtitle, api_base_url, contact_info and doc_url, and turns
registration_enabled, email_verify_enabled, invitation_code_enabled and
turnstile_enabled off. turnstile_enabled alone gates the captcha on login,
register, forgot-password and both verify-code endpoints, and
email_verify_enabled is a precondition of IsPasswordResetEnabled.
The damage is easy to miss. site_name has a built-in fallback, so
getStringOrDefault renders the cleared value as the default product name and the
login page visibly changes, while the toggles just go quiet. Reopening the
settings page reads the already-cleared state back into the form, so correcting
the one visible field and saving persists the rest of the damage.
Fields that grew their own guard already survive this: the SMTP block falls back
to the previous values when smtp_host arrives empty, secret fields are written
only when non-empty, and 132 request fields are pointers whose handler merges an
omitted field with the stored value. This generalizes that pattern rather than
adding a fourth ad-hoc guard.
The handler now decodes the payload a second time as a raw field map, resolves
the setting key each absent field would have written, and hands that set to the
service, which drops those keys before SetMultiple, so the stored value is never
touched. Fields the payload does carry are written as before, giving the caller
the partial-update semantics it was already assuming. The mapping is reflected off
the request's json tags so new fields are covered without maintaining a list;
smtp_from_email is the only field whose json name differs from its setting key
and is aliased explicitly.
Only value-typed fields are filtered. Pointer fields keep whole-document
behaviour on purpose: forwarded_client_ip_headers and
api_key_acl_trust_forwarded_ip depend on being rewritten on every save to
re-normalize fail-closed state, which the malformed forwarded-client-IP header
test pins down.
An explicitly sent empty value is still a deliberate clear; only absent fields
are preserved. A partial write refreshes the in-process caches from storage
instead of from the request struct, which holds zero values for whatever the
caller omitted.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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