Post-merge audit found 6 adjacent variants of the VERIA-28 class. All
fixed here with regression tests:
1. Strip widened from 3 named keys to the full user_api_key_* prefix.
The proxy writes a dozen user_api_key_* fields (user_id, alias,
spend, team_id, request_route, end_user_id, …) into
data[_metadata_variable_name]; the 3-key strip left the rest
exploitable for identity/spend forgery in audit logs and guardrails.
2. proxy_server_request['body'] snapshot moved to AFTER the strip.
Was captured at line ~990 before the strip ran, so
standard_logging_object, lago, and spend_tracking readers saw the
attacker-forged payload even though the live data dict was clean.
3. get_tags_from_request_body (auth-time) now coerces JSON-string
metadata via safe_json_loads. Previously crashed with
AttributeError on string metadata (DoS; potential RBAC bypass if
a caller swallowed the exception).
4. get_end_user_id_from_request_body coerces JSON-string
metadata/litellm_metadata. Previously isinstance(dict) guard
caused end-user budget attribution to be silently skipped when
the caller sent metadata as a JSON string.
5. Four hand-rolled 'if data.get("metadata") is None: data["metadata"] = {}'
blocks in proxy_server.py (7160, 7341, 7590, 11375) now guard on
isinstance(dict). They crashed with TypeError when metadata was a
JSON string (DoS).
6. _get_admin_metadata defensively guards with isinstance(dict);
previously AttributeError'd on any leaked string metadata.
Also hoists the inline safe_json_loads import in _guardrail_modification_check
to module level per CLAUDE.md style.
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