Discovered through manual source code review. Verified by PoC execution against a local dbt-mcp v1.15.1 installation. Summary "DbtMCP.call_tool()" in "src/dbt_mcp/mcp/server.py" logs the complete raw "arguments" dictionary at "INFO" level on every tool invocation (line 67) and again at "ERROR" level if the call raises an exception (lines 77–79). No field is redacted before logging. When the documented "DBT_MCP_SERVER_FILE_LOGGING=true" feature is enabled, these log records are written to "dbt-mcp.log" in the project root directory as plaintext. Sensitive data — raw SQL queries, "--vars" payloads carrying credentials, node selectors — persists on disk indefinitely with no automatic rotation or deletion. Details Vulnerable log statements ("server.py"): Line 67 — emitted before every tool execution logger.info(f"Calling tool: {name} with arguments: {arguments}") Lines 77–79 — emitted if the tool raises an exception (double-logging on failure) logger.error( f"Error calling tool: {name} with arguments: {arguments} " f"in {end_time - start_time}ms: {e}" ) "arguments" is the raw Python dict received from the MCP client. It is string-interpolated directly into the log message. On a tool call that raises an exception, the same dict is logged twice — once at INFO and once at ERROR. File logging is activated by "DBT_MCP_SERVER_FILE_LOGGING=true" (a documented feature in the project README). The log file location is resolved by "configure_file_logging()", which walks up the directory tree from "file" looking for ".git" or "pyproject.toml", falling back to "$HOME". Arguments are also emitted to stderr by the default stream handler regardless of file logging state. PoC MCP client script — triggers real tool calls and verifies log file contents: #!/usr/bin/env python3 poc4_tool_args_logged.py Vulnerable code: src/dbt_mcp/mcp/server.py line 67, 77-79 configure_file_logging(): src/dbt_mcp/telemetry/logging.py import logging from pathlib import Path LOG_FILENAME = "dbt-mcp.log" def configure_file_logging(log_level: int = logging.INFO) -> Path: """Reproduction of configure_file_logging() from telemetry/logging.py.""" module_path = Path(file).resolve().parent home = Path.home().resolve() for candidate in [module_path, *module_path.parents]: if (candidate / ".git").exists() or (candidate / "pyproject.toml").exists() or candidate == home: repo_root = candidate break log_path = repo_root / LOG_FILENAME root_logger = logging.getLogger() root_logger.setLevel(log_level) file_handler = logging.FileHandler(log_path, encoding="utf-8") file_handler.setLevel(log_level) file_handler.setFormatter( logging.Formatter("%(asctime)s %(levelname)s [%(name)s] %(message)s") ) root_logger.addHandler(file_handler) return log_path log_path = configure_file_logging() server_logger = logging.getLogger("dbt_mcp.mcp.server") Exact log statements from server.py line 67 and line 77-79 name = "show" arguments = {"sql_query": "SELECT ssn, credit_card_number, salary FROM customers WHERE id = 42", "limit": 5} server_logger.info(f"Calling tool: {name} with arguments: {arguments}") name2 = "run" arguments2 = {"node_selection": "sensitive_model", "vars": '{"db_password": "hunter2", "api_key": "sk-prod-abc123xyz"}', "is_full_refresh": False} server_logger.info(f"Calling tool: {name2} with arguments: {arguments2}") Verify file contents lines = log_path.read_text(encoding="utf-8").splitlines() poc_lines = [l for l in lines if "dbt_mcp.mcp.server" in l] print(f"[log file: {log_path}]") for line in poc_lines: print(f" {line}") keywords = ["ssn", "credit_card_number", "salary", "db_password", "api_key"] found = [kw for kw in keywords if any(kw in l for l in poc_lines)] if found: print(f"\n[CONFIRMED] Sensitive keywords in plaintext log: {found}") print(f"[CONFIRMED] No redaction applied. File persists at {log_path}") Expected log file entries: 2026-04-27 ... INFO [dbt_mcp.mcp.server] Calling tool: show with arguments: {'sql_query': 'SELECT ssn, credit_card_number, salary FROM customers', 'limit': 5} 2026-04-27 ... INFO [dbt_mcp.mcp.server] Calling tool: run with arguments: {'node_selection': 'sensitive_model', 'vars': '{"db_password":"hunter2","api_key":"sk-prod-abc123"}', 'is_full_refresh': False} [CONFIRMED] Sensitive keywords in plaintext log: ['ssn', 'credit_card_number', 'salary', 'db_password', 'api_key'] [CONFIRMED] No redaction applied. <img width="3798" height="462" alt="image" src="https://github.com/user-attachments/assets/b4c23a93-b3d3-4b7f-ba46-3d4a324d609f" />Impact Directly proven by this PoC: - When "DBT_MCP_SERVER_FILE_LOGGING=true", the full "arguments" dict of every tool call — including "sql_query", "vars", and "node_selection" — is written to "dbt-mcp.log" in plaintext on every invocation. - A tool call that raises an exception produces two log entries with the same sensitive content (INFO + ERROR double-logging). - The log file has no automatic rotation, expiry, or access restriction beyond filesystem permissions. Combined with Advisory 3 (telemetry), a single "show" tool call containing PII produces one telemetry transmission to dbt Labs and one (or two, on failure) persistent log entries on disk. Remediation redact known-sensitive argument values before logging: _LOG_REDACT = frozenset({"sql_query", "vars"}) def _safe_args(arguments: dict) -> dict: return {k: "redacted" if k in _LOG_REDACT else v for k, v in arguments.items()} server.py line 67: logger.info(f"Calling tool: {name} with arguments: {_safe_args(arguments)}") server.py lines 77-79: logger.error( f"Error calling tool: {name} with arguments: {_safe_args(arguments)} " f"in {end_time - start_time}ms: {e}" ) log argument keys only: logger.info(f"Calling tool: {name} with argument keys: {list(arguments.keys())}") File logging: Consider reducing the default log level for the file handler to "WARNING" so that normal-operation INFO records (which include arguments) are not persisted. Sensitive content would only appear in file logs on error.