fix(security): validate ticker before using as path component (#618)

The ticker symbol reaches three filesystem-path construction sites
(load_ohlcv cache filename, checkpointer DB path, _log_state results
directory) without validation. A value containing path separators or
"../" escapes the configured cache / checkpoints / results directory.

Two attack vectors:
- Programmatic callers passing arbitrary ticker to propagate()
- Prompt injection via fetched news content steering the LLM into
  tool calls with attacker-chosen ticker

Fix: new safe_ticker_component() validator in tradingagents/dataflows/
utils.py applied at all three sites. Allows the standard ticker
character set ([A-Za-z0-9._\-\^], up to 32 chars) and explicitly
rejects dot-only values like "." and ".." which would otherwise pass
the regex but traverse parent directories. Seven test cases cover
the accepted formats (BRK-B, 7203.T, ^GSPC, etc.) and the rejected
inputs (path separators, null bytes, whitespace, empty values,
overlong strings, dot-only values).

Closes #618.

tradingagents/dataflows/stockstats_utils.py

@@ -8,6 +8,7 @@ from stockstats import wrap
 from typing import Annotated
 import os
 from .config import get_config
+from .utils import safe_ticker_component
 
 logger = logging.getLogger(__name__)
 
@@ -51,6 +52,10 @@ def load_ohlcv(symbol: str, curr_date: str) -> pd.DataFrame:
     subsequent calls the cache is reused. Rows after curr_date are
     filtered out so backtests never see future prices.
     """
+    # Reject ticker values that would escape the cache directory when
+    # interpolated into the cache filename (e.g. ``../../tmp/x``).
+    safe_symbol = safe_ticker_component(symbol)
+
     config = get_config()
     curr_date_dt = pd.to_datetime(curr_date)
 
@@ -63,7 +68,7 @@ def load_ohlcv(symbol: str, curr_date: str) -> pd.DataFrame:
     os.makedirs(config["data_cache_dir"], exist_ok=True)
     data_file = os.path.join(
         config["data_cache_dir"],
-        f"{symbol}-YFin-data-{start_str}-{end_str}.csv",
+        f"{safe_symbol}-YFin-data-{start_str}-{end_str}.csv",
     )
 
     if os.path.exists(data_file):

tradingagents/dataflows/utils.py

@@ -1,4 +1,5 @@
 import os
+import re
 import json
 import pandas as pd
 from datetime import date, timedelta, datetime
@@ -6,6 +7,40 @@ from typing import Annotated
 
 SavePathType = Annotated[str, "File path to save data. If None, data is not saved."]
 
+# Tickers can contain letters, digits, dot, dash, underscore, and caret
+# (for index symbols like ^GSPC). Anything else is rejected so the value
+# never escapes a containing directory when interpolated into a path.
+_TICKER_PATH_RE = re.compile(r"^[A-Za-z0-9._\-\^]+$")
+
+
+def safe_ticker_component(value: str, *, max_len: int = 32) -> str:
+    """Validate ``value`` is safe to interpolate into a filesystem path.
+
+    Tickers come from user CLI input or from LLM tool calls, both of which
+    can be influenced by attacker-controlled content (e.g. prompt injection
+    embedded in fetched news). Without validation, a value like
+    ``"../../../etc/foo"`` flows into ``os.path.join`` / ``Path /`` and
+    escapes the configured cache, checkpoint, or results directory.
+
+    Returns ``value`` unchanged when it matches the allowed pattern; raises
+    ``ValueError`` otherwise.
+    """
+    if not isinstance(value, str) or not value:
+        raise ValueError(f"ticker must be a non-empty string, got {value!r}")
+    if len(value) > max_len:
+        raise ValueError(f"ticker exceeds {max_len} chars: {value!r}")
+    if not _TICKER_PATH_RE.fullmatch(value):
+        raise ValueError(
+            f"ticker contains characters not allowed in a filesystem path: {value!r}"
+        )
+    # The regex above allows '.', so values like '.', '..', '...' would pass,
+    # and as a path component they traverse the parent directory. Reject any
+    # value that's only dots.
+    if set(value) == {"."}:
+        raise ValueError(f"ticker cannot consist solely of dots: {value!r}")
+    return value
+
+
 def save_output(data: pd.DataFrame, tag: str, save_path: SavePathType = None) -> None:
     if save_path:
         data.to_csv(save_path, encoding="utf-8")